Lyngby a Soil Extracts

8/10/2019 Lyngby a Soil Extracts

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The effect of soil extracts on the physiology of

Lyngbya majuscula(Cyanophyta)

Simon Albert

Thesis submitted to the Department of Botany, University of Queensland

as partial fulfilment of BScApp (Env) (Hons)

Supervisors: Dr. Judith O'Neil

A/Prof. William Dennison

Dr. Phil Moody


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Abstract

Recent outbreaks of the cyanobacterium Lyngbya majuscula in Moreton Bay,

Queensland, Australia, have been the impetus for a number of studies to determine

potential triggers for the blooms. The current study assesses the potential for runoff from

various land uses to stimulate the growth of L. majuscula. Soil extracts from eight

representative land uses (including Melaleuca forest, mangroves, pine plantation and

canal development) within the Pumicestone catchment were produced to simulate runoff

events. A biological assay technique was used to determine the potential of each extract

to stimulate L. majuscula productivity. A 102% increase in photosynthetic rate was

recorded (using PAM fluorescence) in response to the cleared pine forest soils. A

significant response was also observed from the forested pine forest soils, with a 33%

increase in photosynthetic rate. Concomitant increases in the concentration of the

photosynthetic pigment phycoerythrin, may explain this result. These results were

consistent across a series of experiments, withL. majusculacollected from two different

sites (Eastern Banks and Deception Bay), both showing significant stimulation in

response to the cleared pine soil extract. Phosphorous concentrations in the pine soil

extracts were an order of magnitude higher than the other soil extracts measured, and

were also acidic (pH 3.5-4). Based on spectral and chemical analyses, the forested (Pine

andMelaleuca) soils have high organic carbon and soluble iron content. Parallel studies

indicate these organic rich soil extracts are able to strongly complex iron, providing a

potential transport mechanism for bioavailable iron from the land to reach the L.

majuscula, in the marine environment. The link made by the current study between

catchment derived compounds and blooms of L. majuscula in Moreton Bay, provides a

focus for potential management actions.


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Introduction

Lyngbya majusculais a toxic, filamentous marine cyanobacteria within theOscillatoriacea,

previously cited in literature asMicrocoleus lyngbyaceus(Ktzing)(Diaz et al. 1990,

Speziale & Dyck 1992). L. majusculagrows on solid substrates or epiphytically onseagrass in the coastal zones of many sub-tropical and tropical oceans. Since the early

1990s nuisance blooms of this toxic cyanobacteria have been occurring seasonally in

Moreton Bay, Queensland, Australia (Dennison et al. 1997). While present in small

quantities in many locations throughout Moreton Bay, theL. majusculabloom events

over the past five years have been both temporally and spatially specific, with Deception

Bay (northern section of Moreton Bay) and the Eastern Banks being the two major bloom

regions.

Lyngbya majusculablooms typically begin in Moreton Bay in the summer

(December/January) and expand rapidly over the following few months to an area up to

10 km2(Dennison et al. 1997). This is often followed by a rapid population collapse,

possibly aided by viruses (Hewson et al. 2001). During this cycle it has been observed

that theL. majusculabegins growth from the sediment below the seagrass canopy. As

the 'bloom' develops this benthic mat is able to grow sufficiently to overtop the seagrass

species, with a blanketing effect that can turn anoxic. After continuous periods of high

light, warm temperatures and calm weather the photosynthetic rates of theL. majuscula

mats are sufficiently high to form large amounts of buoyant bubbles within theL.

majusculamatrix. The benthic mats eventually float to the surface of the water and float

freely. This stage may provide a dispersal mechanism for theL. majusucla, enabling it to

spread into other regions of the bay.

Seagrass loss and altered marine plant community structure have been the most

significant initial impacts ofLyngbya majusculabloom events (Watkinson 2000) to date,

while impacts on biota (particularly turtle and dugong) remain unclear. In addition to

these environmental effects,L. majusculacan have human health impacts. The suite of

toxins withinL. majusculacan cause severe skin and eye irritation as well as asthma like

symptoms (Osborne et al. 2001). The potential for serious deleterious environmental and


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human impacts fromL. majusculain Moreton Bay has provided the impetus for a series

of studies to determine potential limiting factors for these blooms.

In general, marine plants within Moreton Bay are nitrogen limited (O'Donohue &

Dennison 1997, Udy & Dennison 1997). Nitrogen limited systems often favour

prokaryotic nitrogen fixers such as cyanobacteria. In the absence of nitrogen limitation,

iron becomes a major limiting factor of biological growth in oceanic systems (Martin &

Gordon 1988, Martin et al. 1990). More recently this has also been found to be the case

in coastal and estuarine ecosystems (Hutchins & Bruland 1998, Hutchins et al. 1998). In

most aquatic environments, cyanobacteria have a high demand for iron (Paerl et al. 1994,

Trick et al. 1995) and phosphorus (Paerl et al. 1987, Sanudo-Wilhelmy et al 2001) for

both photosynthesis and nitrogen fixation. Elevated iron concentrations in laboratory

studies have: increased productivity and phycocyanin production in Oscillatoria tenius(Trick et al. 1995), elevated nitrogen fixation in Trichodesmium sp.(Rueter et al. 1990)

andincreased toxin production byMicrocystis aeruginosa(Utkilen & Gjolme 1995).

Iron is one of the most abundant elements on earth, however its insolubility at seawater

pH prevents its availability to marine organisms in most instances (Anderson and Morel

1982). At seawater pH, ferric iron (Fe(III)) is the thermodynamically preferred form,

with free Fe(II) undergoing rapid oxidation and subsequent precipitation of the ferricform (Byrne & Kester 1976). Cyanobacteria are unable to take up and utilize these

oxides of iron. This oxidation is generally reduced in the presence of organic ligands that

form a complex with the soluble iron making it more persistent in seawater (Emmenegger

et al. 1998, Santana-Casiano et al. 2000). Following reductive processes (e.g. photo-

reduction) to break this complex (Waite & Morel 1984, Wells & Mayer 1991, Voelker et

al. 1997), phytoplankton and cyanobacteria are able to take up soluble iron directly from

the water column (Anderson & Morel 1982). Therefore, the level of bioavailable iron in

seawater can fluctuate greatly depending on the presence of natural complexation agents

such as organics.

Dissolved organic carbon is a natural feature of Australian coastal waters (Kirk 1994),

particularly those areas surrounded by natural vegetation. The leaves ofMelaleuca,

Acaciaand other lowland vegetation, contain a high proportion of organic carbon (Zoete


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2001). These organics leach from decomposing leaves during rainfall and are either

recycled within the soil system or may be mobilised into the surrounding creeks (Kirk

1994). The organic acids contained within organic-rich terrestrial run-off have been

shown to have strong iron complexation properties (Kuma et al.1996, Matsunaga et al.

1999, Rose et al. unpub. data). Plumes of darkly stained, organic-rich waters have beenobserved entering regions surroundingL. majusculabloom areas in Deception Bay,

particularly following rainfall events and the clearfelling of exotic plantation pine.

Parallel studies investigating the role these organic-rich compounds have as a transport

mechanism for bio-available iron to reach the bloom sites from terrestrial sources, are

currently under way

Coastal waters such as rivers, dams, estuaries are often subject to algal blooms as a resultof nutrient input from terrestrial sources (Mallin et al. 1993). Rivers running through

urbanised catchments generally provide high nutrient loadings as a result of the complex

array of inputs. Forested, undisturbed catchments, generally yield lower water volumes

and more stable, low fluxes of nutrients, reflecting the inherently low nutrient status of

Australian soils (Wild 1958, Beadle 1962, Cambell 1975). Logging of these forests can

greatly alter both water quality and quantity in the surrounding estuaries (Cambell &

Doeg 1989, Rask et al. 1998,Bubb 2000, Roberts 2000), triggering ecological changes

such as algal blooms.

The current study aims to assess the potential for various land uses within the

Pumicestone catchment to be the source of substances stimulating benthic blooms of

Lyngbya majusculain Deception Bay. Although there are many interactive factors,

identifying identifying the potential causal processes of the bloom, in terms of land use

may help explain recent increases in this noxious cyanobacteria. Thus, rather than purely

scientific knowledge of the nutritional requirement ofL. majuscula, this study helps to

provide a more applied and currently much needed result; management focus.


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Study Area

The study was conducted in Moreton Bay, Queensland at two locations, Deception Bay

(27 05 S, 153 09 E) and Eastern Banks (27 26S, 153 24E ) (Figure 1). The

primary focus was in Deception bay and the surrounding catchment (Figure 2). Thecoastal system in whichLyngbya majuscula is blooming in Deception Bay is primarily

influenced by a large estuarine passage (Pumicestone Passage) dividing Bribie Island to

the east and the mainland to the west. This passage is in turn fed by 8-10 creeks and

numerous smaller tributaries draining both mainland and island regions. Much of this

area is low-lying and, hence, the catchment boundary is large.

The Pumicestone catchment contains a diversity of horticultural, residential and natural

land uses. The dominant land use within the Pumicestone catchment is exotic pine

plantations(Pinus elliottii) (39%). Other horticultural activities in the Pumicestone

catchment include; sugar cane, strawberries and the remnants of the largest citrus orchard

in the southern hemisphere (Roy family 1960s). Residential areas are primarily

restricted to the dense canal estates on the southern section of Bribie Island and the

adjacent Sandstone Point on the mainland.

Figure 1:Satellite imagery depicting sampling regions in relation to Australian and Queensland coastlines.

Moreton

Bay

Eastern

Banks

Deception

Bay


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Figure 2:Satellite imagery depicting sampling sites in the Pumicestone catchment.

# Site Site Description

1 Cleared Pine Sandy podosol, Pinus elliottiiplantation cleared ca. 6 months prior to sampling

2 Intact Pine Sandy podosol sampled from mature stand of Pinus elliottii

3 Melaleuca Sandy podosol sampled from mixed forest ofMelaleucaandAcaciaspecies

4 Mangrove Mangrove sediment sampled within anAvicennia marinacommunity

5 Shirley Creek Sediment sampled from this visibly iron rich creek

6 Sandstone Point Intertidal marine Sands overlying Landsborough sandstone bedrock

7 Canal Development Sandy hydrosol sampled from previously dug canal development

8 Coffee Rock Exposed coffee rock layer in intertidal area of Pumicestone Passage

9 Mellum Creek Creek draining mainland regions of pine plantation

10Pine drain Small earth drain between pine plantation plots on Bribie Is.

Table 1:Description of sampling sites within the Pumicestone catchment region.

4 6

8

5

7

21

3

PumicestonePassage

BribieIsland

Bloom Site

9

10


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Methods

A bioassay technique was developed using soil extracts from eight representative land

uses (Melaleucaforest, mangroves, cleared and intact pine plantation, canal development,

iron rich creek, marine sediment and coffee rock) within the Pumicestone catchment

(Table 1). These soil extracts were produced to simulate the compounds that these soils

would yield during natural runoff events. Lyngbya majusculawas incubated in dilutions

of these extracts to determine the physiological effects. Secondly, different dilutions of

selected extracts will be used to determine if a concentration threshold exists forL.

majusculastimulation. Thirdly,L. majuscula from different regions of Moreton Bay was

incubated with selected extracts to determine if the two populations respond similarly.

Soil extract production

Various methods exist for deriving soil extracts. Commonly they are derived through

wetting of intact soil cores until field capacity is reached, to simulate the waterlogging

effect of heavy rainfall. Intact cores are then leached using rainwater for varying periods

of time (up to 40 weeks in some studies) (Khomutova et al. 2000). Although this study

has modified this protocol, comparative studies using leached cores at these sites have

yielded chemically similar extracts (Moody unpub. data).

At sites 1-8, three 400 mm x 90 mm diameter cores of the soil were taken using

polycarbonate corers driven into the ground (Figure 3). The three cores were combined

to reduce spatial variation and the soil structure homogenised. Three kilograms of each

soil type was then mixed with three litres of rainwater and stirred vigorously to produce a

muddy consistency. The mixture was then left in a dark aerobic environment for 24

hours to simulate the water-logging of soil following rainfall. The supernatant was then

decanted off and vacuum filtered through 10 m polycarbonate filters to produce a soil

solution to simulate naturally occurring run-off (Figure 3).


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Bioassays

Bioassays usingLyngbya majusculawere carried out to investigate what effect extracts

from these different land uses had on physiological parameters.

Figure 3:Conceptualisation of methodology used to create soil extracts and assess their effects upon

Lyngbyamajusculaphysiology.

Bioassay of eight primary land uses

Three replicate one-litre glass beakers were filled with 900 ml seawater from the

Deception Bay bloom area and 100 ml (1:9) of the eight soil solutions, 100 mls of

rainwater was added to the seawater control to ensure consistent salinity (3x9 = 27

beakers). This dilution was based on previous salinity monitoring of the bloom region

indicating a 10% decrease in salinity prior to bloom initiation (Watkinson 2000). Five

cm3ofLyngbya majusculawas incubated in these solutions beakers over two days under

50% shadecloth. Various physical and biological parameters were assessed over this

incubation period to assess how the extracts affectedL. majusculaphysiology.


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Bioassay of various extract dilutions

The basic protocol from experiment 1 was replicated. Based on results from the first

experiment, cleared pine, sandstone point and coffee rock extracts were focussed on for

further analysis in this second experiment. Rather than the previous addition of 100 ml ofsoil extract with 900 ml of seawater, 50 ml (1:20), 100 ml (1:10) and 150ml (1:7)

additions of the three extracts were added to 900 ml of seawater. To ensure consistent

salinity, 100 ml and 50ml of rainwater were added to the 50 ml and 100 ml dilutions

respectively. The control consisted of 150 ml of rainwater and 900 ml of seawater.

Bioassay usingLyngbya majusculafrom different sites

Again the basic protocol from experiment 1 was replicated. 100 ml additions of cleared

pine and coffee rock extracts were added with either seawater andL. majuscula from the

Deception Bay bloom site or seawater andL. majusculafrom the Eastern banks bloom

site.

These three bioassays were conducted for two days each over a fourteen-day period in

January 2001. Prior to addition the extracts were analysed for ammonia, nitrogen oxides,

phosphorus, dissolved and total organic carbon, dissolved and total iron, pH and spectral

properties. L. majusculafrom these treatments was analysed for photosynthetic capacity

and photosynthetic pigment (chlorophyll a and phycoerythrin) concentration. During the

incubations the seawater was analysed for ammonia, nitrogen oxides and phosphorus.

Photosynthetic capacity

After 48 hours of incubation a WALZ diving PAM (Pulse Amplitude Modulated)

flourometer was used to measure photosynthetic capacity. Rapid light curves (RLC)

were used to assess the photosynthetic status of theLyngbya majusculaas described

previously (White & Critchley 1999). Each rapid light curve consists of nine saturating

light pulses (0.8 s) separated by an actinic light. This 10 s actinic light increased stepwise

from 9 to 1667 !mol quanta m-2

h-1

. At each of these nine steps electron transport rate


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(ETR) is calculated and plotted against photosynthetically active radiation (PAR) to

produce the RLC.

ETR = Fv/Fm x PAR x 0.5 x 0.84

Fv = Variable florescence

Fm = Maximum florescence

PAR = Photosynthetically active radiation (umol quanta m-2

s-1

)

(White & Chritchley 1999)

Pigment analysis

Both chlorophyll a (chl a) and phycoerythrin (PE) concentrations were assessed after 48

hours of incubation. 0.1g (wet wt.) ofL. majusculatissue was taken and rinsed in filtered

seawater to remove any sediment/particles followed by a rinse in an isotonic solution of

6% ammonium formate to remove excess salts. L. majusculatissue from each incubation

chamber was sampled for both PE and chl aand frozen immediately.

Phycoerythrin

For PE analysis theL. majusculatissue samples were ground in a pestle and mortar using

a phosphate buffer solution (pH 6.5, Buffer value 0.024 - 50% 0.01M KH2PO4 13.9%

0.01M NaOH, 36.1% distilled water). This extract was then transferred to a 15ml

centrifuge tube and made up to 10ml with the buffer solution and extracted overnight.

Following centrifugation at 2500 rpm for 20mins, the supernatant was transferred to a

quartz curvette. Pigment determination was then conducted spectrophotometrically using

absorbance at 565 and 750 as indicators of PE concentration and turbidity respectively.

Using specific phycoerythrin formulas (Rowan 1989) phycoerythrin concentration as a

function of dry tissue weight was then determined using a previously calculated Wet

weight : Dry weight ratio.

Chlorophylla

For Chl aanalysis theL. majusculatissue samples were ground in a pestle and mortar

using 90% Acetone. This extract was then transferred to a 15ml centrifuge tube and


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made up to 10ml with the buffer solution and extracted overnight. Following

centrifugation at 2500 rpm for 20mins then supernatant was transferred to a quartz

curvette. Pigment determination was then conducted spectrophotometrically using

absorbance at 664 and 750 as indicators of chlorophyll aconcentration and turbidity

respectively. Using formulas derived from Parsons et al. (1984) concentration as afunction of dry tissue weight was then determined.

Extract Analysis

Soluble and total iron were analysed using inductively couple plasma atomic emission

spectrometry (ICP-AES). Soluble iron is that which passed through a 0.45M GF/F

filter. Extract pH was assessed using a pH probe attached to a 90-FL Field Lab (TPS).

Dissolved and total organic carbon were assessed using by wet oxidation with sodium

persulphate on a total carbon analyser. Seawater samples for nutrient analysis were

filtered through a 0.45 um filter prior to NOx, NH4and PO4 (FRP) analysis using a

automated LACHAT 8000QC flow injection analyser (FIA).

Spectral Analysis

Water samples were collected from Mellum Creek and an earthern drain in a pine

plantation (sites 9 and 10) both before and after a heavy rainfall event. Waters were

collected in black plastic 20 L drums and kept chilled prior to analysis (within 12 hours).

50 mls of solution was passed through a sartorius 0.45 M syringe mounted filter unit to

remove particulates. Absorbance spectra were then assessed over 300-800nm (1nm

intervals) through a 5cm path length using a Beckman DU500 scanning

spectrophotometer. To remain consistent with previous studies (Kirk 1976, Longstaff et

al. 2001) gilvin 440 readings were converted to a 1m path length.

Statistical analysis

Cochrans test was used to check that variances were homoscedasic. One-way analysis

of variance (ANOVA) was used to test difference in means between treatments. A post

hoc Tukeys test was used to assess which treatments were significantly different.


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Results

Chemical parameters of soil extracts

Extracts derived from the eight various soil types are diverse in both spectral absorbance

and chemical composition (Table 2). This diversity is a function of both soil type and

land use at the sites. The three podosol soil extracts (cleared pine, intact pine and

Melaleuca) all contained significantly more dissolved organic carbon than the other sites.

This was also reflected by high gilvin(absorbance at 440nm (1m path length)) values.

Different land uses within these podosols also showed variation, with the cleared pine

yielding higher dissolved organic carbon than the nativeMelaleucaforest.

The soil extracts can be categorised into two distinct groups based on pH (Table 2). Thethree forested sites (cleared pine, intact pine,Melaleuca) and the canal development all

yielded acidic extracts ranging from pH 3.3 - 4.3. The remainder of the sites yielded

neutral extracts of pH 5.9 - 6.8.

Large variations in free reactive phosphorus (FRP) concentration occurred between the

extracts, cleared pine and intact pine extracts contained 6.7 and 9.5 "M P respectively.

The remaining extracts contained negligible FRP concentrations of 0.05 - 0.3 "M P

(Table 2).

Extract pH Gilvin(g440)

[PO4](M)

DOCmg/L

TOCmg/L

SolubleFe mg/L

Total Femg/L

Fe(sol):Fe(tot)

Cleared Pine 3.9 59.5 6.7 62.9 1270 0.57 1.1 0.50

Intact Pine 3.3 36.9 9.5 35.8 1490 0.12 1.0 0.12

Melaleuca 4.3 36.9 0.3 59.1 255 0.43 2.8 0.15

Mangrove 6.1 1.9


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Large variation in total iron occurred between the extracts, with Shirley Creek yielding

43 mg/L Fe and others between 0.99 mg/L (intact pine) and 6.1mg/L (coffee rock) (Table

2). The concentration of soluble iron however, did not follow these same trends. Shirley

Creek yielded only 0.05 mg/L of soluble iron, whilst cleared pine extract contained 0.57

mg/L soluble. Fe. When the proportion of soluble:total iron is considered, the threeforested sites (cleared pine, intact pine andMelaleuca) had high proportions of dissolved,

0.50, 0.12 and 0.12 respectively. Other extracts had low ratios of between 0 and 0.05

Soluble:Total Fe. The high ratios of soluble iron in the forested sites generally correlated

with the dissolved organic carbon content of the extracts as well (Figure 4, R2= 0.78).

R2= 0.7834

0

0.1

0.2

0.3

0.4

0.5

0.6

0 10 20 30 40 50 60 70

Disolved organic carbon (mg/L)

Solubleiron(mg/L)

Figure 4:The correlation between dissolved organic carbon (DOC) and soluble iron within the eight soil

extracts.

Bioassay results from eight primary land uses

Nutrient Uptake

Uptake rates of phosphorus byLyngbya majusculawhere generally low, with rates of

between 0.01 and 0.06 uM P h-1

in most of the incubation chambers (Table 3). Chambers

with coffee rock, cleared pine and canal development extracts had higher uptake rates of

0.90, 0.17 and 0.13 P uM h-1

respectively (Table 3). Similarly, nitrogen oxides were

assimilated at rates of between 0.05 and 0.17 uM NOx h-1 (Table 3) in most of the

incubation chambers. Chambers with coffee rock, canal development and cleared pine

extracts had elevated uptake rates of 0.51, 0.30 and 0.25 uM NOxh-1

respectively (Table

3). Changes in ammonia concentrations within the incubation chambers were more


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variable between treatments. Uptake rates in the seawater control, intact pine,Melaleuca

and mangrove were between 0.12 and 0.21 uM NH4h-1

(Table 3). Higher rates of 0.39

and 0.66 uM NH4 h-1

occurred in the Sandstone Point and Sandstone+ Pine incubations

respectively. Negligible rates of 0.02 and 0.05 NH4uM h-1

occurred in response to the

Shirley Creek. and canal development extracts, and release of ammonia occurred in thecleared pine and coffee rock chambers at rates of 0.04 and 0.47 NH4uM h

-1respectively

(Table 3).

Extract Phosphorus(M h

-1)

Nitrogen Oxides(M h

-1)

Ammonia(M h

-1)

Seawater Control 0.05 0.11 0.19

Cleared Pine 0.17 0.25 -0.04

Intact Pine 0.01 0.13 0.12

Melaleuca 0.01 0.05 0.21

Mangrove 0.02 0.11 0.15

Shirley Crk. 0.05 0.17 0.02

Sandstone Pt. 0.06 0.10 0.39

Canal Dev. 0.13 0.30 0.05

Coffee Rock 0.90 0.51 -0.47

Sandstone Pt. +

Pine0.01 0.10 0.66

Table 3:Phosphorus, nitrogen oxides and ammonia uptake rates from the various incubations over the first

3 hours afterLyngbya majusculaaddition.


The electron transport rate ofLyngbya majusculausing PAM florescence has been used

to indicate photosynthetic capacity. TheL. majusculain the seawater control had an

electron transport rate of 189 "mol m-2

s-1

(Figure 5). The electron transport rate in

response to cleared pine extract was more than doubled (381 "mol m-2

s-1

), intact pine

showed a 33% increae (252 "mol m-2s-1) and the combination of sandstone point and

pine extracts caused a 74% (329 "mol m-2

s-1

) elevation (p0.05).


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0

50

100

150

200

250

300

350

400

450

SeawaterControl

ClearedPine

IntactPine

Melaleuca

Mangrove

ShirleyCreek

SandstonePoint

CanalDevelopment

CoffeeRock

Sandstone+Pine

Soil Extract

Photosyntheticcapacity

ETRmax.

(umolm

-2s

-1)

p0.05). Large variability in phycoerythrin concentrations inL. majuscula

occurred in response to the extracts. All treatments caused an increase in phycoerythrin

concentration, however the only statistically significant (p


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Bioassay results from various extract dilutions

Nutrient uptake

Uptake rates of phosphorus byL. majusculawhere generally low, with rates of between

0.01 and 0.03 uM P h

-1

in most of the incubation chambers (Table 4). Chambers with the1:20, 1:10, 1:7 dilutions of cleared pine extract had higher uptake rates of 0.07, 0.06 and

0.07 P uM h-1

respectively (table 4). Nitrogen oxides in the seawater control were

assimilated at 0.44 uM NOx h-1 (Table 4). The 1:20 dilutions of coffee rock and

sandstone point extract had elevated uptake rates of 0.74 and 0.68 uM NOxh-1

respectively (Table 4). All extracts showed a stepwise decrease in nitrogen oxide uptake

rates with increasing extract concentration. Uptake of ammonia within the incubation

chambers was variable between treatments. A net increase in ammonia concentration

occurred in the seawater control of 0.03 uM NH4h-1

(Table 4). A stepwise increase in

ammonia uptake rate occurred with increasing concentration of coffee rock and sandstone

point extract, to maximal rates of 4.98 and 2.41 uM NH4 h-1

respectively. Net release of

ammonia occurred in response to 1:10 and 1:7 dilutions of cleared pine extract (Table 4).

Extract Phosphorus(M h

-1)

Nitrogen Oxides(M h

-1)

Ammonia(M h

-1)

Seawater Control 0.01 0.44 -0.03

Cleared Pine 1:20 0.07 0.42 0.25

Cleared Pine 1:10 0.06 0.28 -0.13

Cleared Pine 1:7 0.07 0.25 -0.04

Sandstone Pt. 1:20 0.01 0.74 1.90

Sandstone Pt. 1:10 0.01 0.61 3.03

Sandstone Pt. 1:7 0.03 0.53 4.98

Coffee Rock 1:20 0.01 0.68 1.01

Coffee Rock 1:10 0.01 0.43 1.51

Coffee Rock 1:7 0.03 0.28 2.41

Table 4:Phosphorus, nitrogen oxides and ammonia uptake rates from the various incubations over the first

3 hours afterLyngbya majusculaaddition.


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The seawater control had an electron transport rate of 197 "mol m-2

s-1

(Figure 7), similar

to that of the previous experiment (Figure 7). Electron transport rates were elevated in

the 1:10 and 1:7 dilutions of cleared pine extract (275 and 271 "mol m-2

s-1

respectively)

and the combination of sandstone point and pine extracts (380 "mol m-2

s-1

) (p


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sandstone point extracts elevated phycoerythrin concentration to 10.6 mg/g DW (Figure

8). Chlorophyll aconcentrations were not significantly altered by addition of any of the

various soil extracts (Figure 8).

0

2

4

6

8

10

12

14

16

Seawater

Control

Cleared

Pine 1:20

Cleared

Pine 1:10

Cleared

Pine 1:7

Sandstone

Point 1:20

Sandstone

Point 1:10

Sandstone

Point :7

Coffee

Rock 1:20

Coffee

Rock 1:10

Coffee

Rock 1:7

Sandstone

+ Pine

1:1:14

Soi l Ext ract /Di lu t ion

PigmentConcentration(mg/gDW)

Ch lo rophyl l P hyc oe ryt hr inp


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0

50

100

150

200

250

300

350

Seawater

Control

Cleared

Pine

Coffee

Rock

Seawater

Control

Cleared

Pine

Coffee

Rock

Soil Extract

Photosyn

theticcapacity

(ETRma

xumolm

-2s

-1)

p


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Spectral properties of waters

The absorbance of creek waters sampled from the Pumicestone region followed distinct

patterns across the UV-VIS spectrum. The UV(B) region (280-315 nm) shows variable

absorbencies between 0.02 and 0.8. The UV(A) region (315-400 nm) was dominated bya large peak at 295 nm (Figure 11). From 330-750 the absorbance gradually declined. It

is likely that the peak at 390 nm is an aberration of the transition from VIS-UV light

sources within the spectrophotometer. The pine drain had absorbencies twice that of

Mellum Creek across the 400-600 nm range in both dry and wet periods. In both creeks,

there was also a two-fold increase in absorbencies during the high rainfall (wet period)

compared to the low rainfall (dry) period (Figure 11).

0

0.5

1

1.5

2

2.5

3

3.5

200 300 400 500 600 700 800

Wavelength (nm)

Absor

bance(5cmpathlength)

Mellum Crk. (Dry)

Pine Crk. (Wet)

Pine Crk. (Dry)

Mellum Crk. (Wet)

Figure 11:Spectral absorbance (5cm path length) of Mellum Creek and a pine drain before and after a

heavy rainfall event.


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Discussion

Blooms ofLyngbya majusculahave been increasing in the Deception Bay region of

Moreton Bay region over recent years. It is hypothesised that altered runoff dynamics

due to land use change within the catchment may have contributed to these increases.

Runoff during rain events may be releasing iron, phosphorus and dissolved organics,

which have been shown in other regions to stimulate algal blooms (Bennet et al. 1986,

Mallin et al. 1991, 1993). The Pumicestone catchment, which leads into Deception Bay,

contains a diversity of horticultural, residential and natural land uses. The dominant land

use within the catchment is exotic pine plantations(Pinus elliottii) (39%), a third of

which have been clear-felled in the last decade (Figure 12). This current study has

assessed the potential for these various land uses within the Pumicestone catchment to be

the source of substances stimulating blooms ofL. majusculain Deception Bay.

Large variability occurred in the chemical composition of soil extracts derived from the

different land uses. Due to the high capacity for forests to fix atmospheric carbon the

cleared pine, intact pine andMelaleucaforest soils yielded higher organic carbon than

un-forested sites. Differences between forests however are more compelling. Total

organic carbon was higher in the pine forests compared with that of theMelaleuca

forests. These differences have been observed previously over a twelve-week leachingstudy, pine plantations yielded twice the organic carbon as that of a natural oak forest,

and four times that of grasslands (Khomutova et al. 2000). These differences are likely a

product of the lower C: N ratio of pine litter and higher surface area: volume ratio

enabling rapid microbial incorporation into the soil.

Phosphorus generally has a strong affinity for binding to particles, it is generally

considered immobile within soils, and attached to suspended sediment particles in runoff

(Johnson et al. 1976, Duffy et al. 1978). Therefore, the high dissolved phosphorus

concentrations within the cleared and intact pine forest extracts would not generally be

anticipated. However, recent research has shown that in forested catchments phosphorus

is predominately attached to materials


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photoreduction of Fe(II) from these complexes, UV light is also able to drive the release

of orthophosphate from the P-Fe-organic complex (Francko & Heath 1983, Cotner &

Heath 1990). However in the absence of Fe(III), phosphorus shows little affinity for

forming a soluble P-organic complex (Koenings and Hooper 1976).

The forested soils (pine andMelaleuca) yielded acidic extracts between pH 3.5-4.3. This

acidification of forested extracts has been noted previously in leaching trials using intact

soil columns of pine and grassland sites (pH 3.6 and 7.1 respectively) (Khomutova et al.

2000). This acidification allows iron oxides and phosphates present within the soil to

become mobilised. This mobilised iron, in combination with the high organic matter of

these forested soils, would likely yield an iron-organic complex.

Relationship between soluble iron and dissolved organic carbon

In the current study, there was a positive correlation between the soluble iron

concentrations and the organic matter contained in the different soil extracts. Previous

studies have shown that organic carbon from both terrestrial and marine sources is able to

complex with Fe(II) or Fe(III) (Theis and Singer 1974, Koenings & Hooper 1976, Morel

1983). Extracts without high concentrations of organic material, such as Shirley Creek,

had very high total iron but none was present in the soluble phase. Whereas, organic rich

extracts did not necessarily have high total iron content, but a high proportion of what

was there was in the soluble phase. The coffee rock extract was the only exception to this

trend, having high dissolved organic carbon with negligible iron present in the soluble

phase. This is likely due to the difference in the specific organic compounds between the

forested soils and coffee rock. Specific organics types have differing abilities to complex

iron (Hutchins et al. 1999). As only DOC and TOC assessments were made of these

extracts, it is beyond the scope of this study to draw any links between soluble iron and

specific organic types (e.g. fulvic acid etc.). Parallel studies, have indicated that the

organics within the pine extracts are able to complex the iron 240 times the rate of the

organics in the coffee rock extract (Rose unpub. data). Thus, not only are pine forests

yielding more organic rich material into Deception Bay, that organic material is able to

complex iron far more effectively than organics from the native vegetation.


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The acidity of the forest soils shifts the thermodynamic preference towards soluble ferric

iron. Coupled with this, acidification of soils reduces their capacity to absorb organic

matter and hence yields a greater dissolved organic carbon component (Forsberg 1992).

These factors would contribute to the elevated soluble iron in the acidic forest soil

extracts. However, there was no direct correlation (R

2

= 0.0816) between soluble ironand pH. Cultivation of pine forest soils also increases organically bound iron and

aluminium (Dormaar 1979, Zhang 1988). It has been previously noted that soils under

coniferous species such as Pinus elliottiigenerally have high concentrations of

organically bound iron and aluminium (Quideau & Bockheim 1996, Khomutova 2000).

This may be a function of the three above mentioned factors (DOC, pH and cultivation).

Being soluble, these fine colloidal organic-iron complexes may be transported in the

water column. Prior to release of free Fe(II)/Fe(III) a process such as photo-reduction

must occur (Voelker et al. 1997, Waite & Morel 1984, Wells & Mayer 1991). This is

somewhat similar to what has been hypothesised to occur in Deception Bay. The

organics from the pine provide a transport mechanism for the iron to reach the bloom site,

upon reaching the shallow high light environment photo-reduction occurs, releasing bio-

available iron to theL. majuscula. Similar patterns of iron/organic dynamics have been

noted in Swiss freshwater lakes (Emmenegger et al. 1998), where cyanobacterial blooms

have been linked with terrestrial organics providing a source of bioavailable iron.

Soil extract effects on photosynthetic capacity ofLyngbya majuscla

The main focus of this study was to investigate how the soil extracts (from different land

uses) affected physiological parameters ofLyngbya majuscula. A significant (p


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extracts. It appears, based on these results, that a threshold concentration of phosphorus

may be required for elevation of the photosynthetic capacity ofL. majuscula. The

magnitude of this elevation however, may be related to soluble iron concentration not

phosphorus. This pattern is re-enforced by the results obtained fromL. majusculatreated

with the other extracts. TheMelaleuca, mangrove, canal development and coffee rockextracts all contained significantly higher soluble iron than the intact pine extract, yet,

unlike the intact pine, the extracts from these soils contained low phosphorus

concentrations, and hence lacked the photosynthetic response.

These incubations indicate that a combination of iron and phosphorus likely stimulated

the photosynthetic capacity inLyngbya majuscula. These results correlate with studies of

other cyanobacteria and plankton species in which interactions between iron and

phosphorus were required for elevations in photosynthetic rates (Lovstad & Krogstad

2001, Clasen & Bernhard 1974). However, at the Deception Bay bloom site it is

probable that sufficient iron and phosphorus is present in the sediment to supportL.

majusculagrowth and terrestrial sources may not be necessarily important. Thus, it is the

dissolved organic carbon which may become the critical component in complexing the

iron and potentially phosphorus already present on site in the sediment, into the soluble

phase for assimilation byL. majuscula.

Nutrient uptake

TheLyngbya majusculaused, was sampled from waters with very low dissolved [PO4]

and [NH4] (Watkinson 2000). However, when incubated in elevated concentrations, the

uptake of nitrogen (NH4/NOx) and phosphorous was extremely rapid, with the bulk

absorbed within the first hour. It is interesting thatL. majusculaappears to be

assimilating ammonia and nitrogen oxides despite being capable of nitrogen fixation.

During late stages ofLyngbya majusculablooms it has been previously observed that

nitrogen fixation rates decrease compared to earlier stages of the bloom (Duffy & ONeil

submitted). Thus, it would be expected alternate nitrogen sources such as ammonia

would be sought. Indeed, nitrogen fixing cyanobacteria can assimilate ammonia directly

from the water column, particularly during late stages of the growth cycle (Mulholland &

Capone 2000), potentially due to the metabolic costs of nitrogen fixation.


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With increasing concentrations of extract added, the uptake of ammonia increased

concomitantly. This uptake of excess nutrients has been observed previously in

phytoplankton (McCarthy & Goldman 1979). Hypothetically, if nutrient runoff into

Deception Bay were to increase,Lyngbya majusculawould have the capacity to rapidlyassimilate this and potentially increase growth rates.

Land use affects catchment hydrology

The potential for elevated terrestrial nutrient run-off into Deception Bay waters is high,

with large changes in catchment land use in recent years. The Pumicestone catchment

contains a diversity of horticultural, residential and natural land uses. The dominant land

use within the Pumicestone catchment is exotic pine plantations(Pinus elliottii) (39%).

Plantations of exotic P. elliottii within SE Queensland are grown as a monoculture,

predominantly in coastal lowland regions dominated by low nutrient sandy podosol soil.

Within the last 5 years, a third of the total plantation area has been clear-felled, partly as a

result of salvage logging after bushfires in 1995-96 (Figure 12).

Figure 12:Areas of pine plantation clear-felled within the Pumicestone catchment over the last 12 years.

Source: Christian Witte Department of Natural Resources and Mines, Queensland Government.


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The conversion of conventional crops (e.g. sugar cane, orchards) to short rotation woody

plantations (e.g. Pinus sp.) reduces eutrophication of waters and reduces the quantity of

runoff, due to the reduced fertilizer requirements and deeper root penetration of woody

plantations (Joslin et al. 1997). However, the Joslin (1997) study was based during the

growth phase of the plantations and did not consider the impacts of harvesting on waterquality and quantity. Large-scale clear-felling of forests has been shown to elevate

dissolved nutrient concentrations, suspended sediment loadings and net run-off volume

into surrounding waters (Cambell & Doeg 1989).

Mobilisation of organics from forested areas is enhanced following sufficient rainfall to

saturate the soil column. The high evapotranspiration rate within forests is generally

sufficient to maintain the water table below the surface, and hence prevent excess run-off.

However, due to the clear-felling of pine plantations this hydrological balance is upset

such that elevated run-off of organics occurs. Following clear-felling in the Pumicestone

catchment, darkly stained, organic rich waters have been observed entering Pumicestone

passage (Figure 13). It can take 4-8 years after clearing for evapotranspiration to become

sufficient enough to lower the water table (Bubb pers comm.). It is likely that large scale

clearing of any vegetation type within the region will cause similar hydrological changes.

Figure 13:Organic rich waters entering Pumicestone Passage through

WestawaysCreek (Bribie Is.), following pine plantation clear-felling.


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Organic rich run-off into coastal waters

Algal blooms in estuaries worldwide have in many cases been linked to terrestrial run-

off, following periods of heavy rainfall (Bennet et al. 1986, Mallin et al. 1991, 1993).

More specifically, the introduction of dissolved organic matter as a result of this rainfallhas been attributed to phytoplankton blooms (Heil 1996). High levels of dissolved

organic matter are common in the coastal waters of Australia, resulting in stained water

colour in some regions (Kirk 1994, Figure 13). Evidence exists, that the input of organic

material into natural waters has been increasing in some regions across Europe over the

last 15 years (Andersson et al. 1989, Forsberg and Peterson 1990).

Spectral data on creeks entering Pumicestone Passage indicate that high organic loadings

enter the passage from both mainland and Bribie Is. areas. Total organic carbon within

creeks adjacent to pine forests can reach levels up to 28.5 mg/L (Watkinson 2000), far in

excess of background levels. Distinct increases in organic absorbances occurred in

Mellum Creek and a pine drain following a rainfall event in early February. During the

high rainfall period both creeks had gilvin (absorbance at 440nm) readings higher than

that of previous studies of Australian water bodies (Kirk 1976). As explained previously,

heavy rainfall sufficient to saturate the soil column yields high concentration of organics

in the soluble phase.

Long term leaching studies of soil cores from pine forests have shown that after 20

weeks, 50% of the organic carbon is removed through rainfall leaching (Khomutova et al.

2000). After that period leaching slowed considerably. Although conditions may vary in

actual forests, it can be expected that following clear-felling, the majority of organic

carbon will be leached within the first 20-30 weeks. Based on this evidence, potential

management strategies are able to be recommended. One possibility for instance, is that

clear-felling of large areas of pine plantation be conducted in late summer after the

Lyngbya majusculablooms and heavy rainfall periods have subsided. This would allow

the following 20-30 weeks for much of the organic carbon to leach out during the winter

months, when waters are colder, without the threat of promotingL. majusculablooms.

By the following summer, when the waters are warm enough forL. majusculato bloom,


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a cover crop with high transpiration capability could have been planted on the clear-felled

areas, increasing evapotranspiration and further reducing the leaching of remaining

organic matter. Further lab based leaching studies have yielded higher organic carbon

leaching with increasing air temperature (Duffy et al. 1989). This may further compound

the elevated organic carbon leaching into Pumicestone Passage during the warm summermonths.

Dissolved organic carbon effects light quality

Coupled with the iron complexation dynamics, dissolved organic carbon has also been

attributed to a reduction in light quality within the water column. The spectra of sunlight

can be generically divided into ultraviolet (UV-200-400nm), blue (400-500 nm), green

(500-600 nm) and red (600-750 nm) bands. Absorbance spectra of extracts from this

study show high absorbance in blue region of the spectrum. Organics have been

previously shown to absorb primarily in the UV and blue (400-500 nm) regions of the

spectra (Kirk 1976). The parameter gilvin (absorbance at 440nm) has been coined to

characterize the absorbance of these organics. Seawater has a background absorbance of

red light. Thus in seawater containing organic material the majority of light available to

organism is green (500-600 nm). Chlorophyll ahas a primary absorbance peak in the

blue band (Soret band) and a secondary peak in the red band, hence, it is unable to absorb

sufficient light in organic rich waters. L. majuscula, like many cyanobacteria, has a

specialized pigment (phycoerythrin), which has an absorption maxim at 565 nm (green).

This may be an evolutionary adaptation to having to inhabit organic rich waters in order

to receive sufficient iron, giving it a preferential advantage over flora reliant on

chlorophyll a. The impacts of dissolved organics on both chromatic quantity and quality

has been observed previously (Jerlov 1955, Kirk 1976, Grantham 1981, Doering et al.

1994, Kirk 1994, Davies-Colley et al. 1993, Schwarz & Markager 1999)


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Changes in light quality effect cyanobacterial pigments

Red algae (Rhodophyta) are able to increase either chlorophyll or phycoerythrin

production based on the light environment exposed to (Aguirre-von-Wobeser et al. 2001).

Rapid changes in pigment ratios over diurnal cycles in response to changes in light

quality have also been observed (Lopez 1992). More specifically, light quality can

influence photosynthetic pigments and productivity inLyngbya majuscula(Longstaff et

al. 2001). Phycoerythrin concentrations inL. majuscula increased following alteration

of ambient light quality similar to that experienced in Deception Bay as a result of

dissolved organics in the water column. In the current study, a strong correlation was

found between gilvin readings in the extracts and the phycoerythrin concentration of the

L. majuscula. The only exception to this correlation was the lowest addition of cleared

pine extract, which caused high phycoerythrin concentrations despite relatively low

gilvin levels. This anomaly may be due to the fact that the pine extract had high amounts

of soluble iron for phycoerythrin production and was, hence, less controlled by light

quality. This general trend of high phycoerythrin concentrations in water with high gilvin

is supported by comparisons of the Deception Bay and Eastern BanksL. majuscula

controls. Without addition of extracts, theL. majusculafrom Deception Bay had

significantly higher phycoerythrin concentrations than that ofL. majusculafrom the

Eastern Banks, most probably as a result of the spectral differences in the environment

where each had been acclimatised.

Elevated phycoerythrin concentrations ofL. majusculain response to cleared pine

extracts may be enabling the increase in photosynthetic capacity observed due to greater

photon capturing ability. The coffee rock treatment however, had elevated phycoerythrin

concentrations without any apparent effect on photosynthetic capacity. Similar increases

of phycobillins in the pelagic cyanobacterium Trichodesmiumhave been observed

without subsequent photosynthetic increases (Trick et al. 1995). It was hypothesised that

the phycobillins in this instance, were in an inactive state and used only for nitrogen

storage. Previous studies indicate that iron availability can also influence phycoerythrin

concentrations (Sandmann 1985). However, in the current study, the correlation between

soluble iron and phycoerythrin was not evident (R2=0.169).


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Conceptual summary of four extract groupings

(a) (b)

(c) (d)

Figure 14(a,b,c,d):Conceptualisation of interactions between soil extracts, light andLyngbya majuscula

physiology (relative symbol sizes reflect concentrations of various parameters).


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The data derived from this study can be summarized into four distinct groupings based on

land use.

Lyngbya majusculatreated with extracts derived from Sandstone Point and Shirley Creek

sediments received the full sunlight spectrum and thus had equal ratios of phycoerythrinand chlorophyll a. Negligible soluble iron was present in the extracts due to the lack of

organics. This lack of available iron combined with low phosphorus concentrations

limited photosynthetic activity (Figure 14a).

Lyngbya majusculatreated with extracts derived from mangrove and canal development

soils received the full sunlight spectrum and thus had equal ratios of phycoerythrin and

chlorophyll a. The majority of iron was not soluble due to the low organics present. This

low available iron combined with low phosphorus concentrations resulted in limited

photosynthetic activity (Figure 14b).

Lyngbya majusculatreated with coffee rock andMelaleucaextracts received a reduced

spectrum of light due to the dissolved organics filtering out the blue region. This caused

an elevation of the phycoerythrin concentrations relative to chlorophyll. The dissolved

organics complexed some iron into the soluble phase however phosphorus was not

present thus, photosynthetic activity was limited (Figure 14c).

Lyngbya majuscula treated with cleared and intact pine extracts received a reduced

spectrum of light due to the dissolved organics filtering out the blue region. This caused

an elevation of the phycoerythrin concentrations relative to chlorophyll. Dissolved

organics complexed large amounts of iron into the soluble phase. High concentrations of

phosphorus coupled with this available iron caused an elevation in photosynthetic

capacity (Figure 14d). Coupled with the potential for pine forest soils to stimulateL.

majuscula growth, are the increased loadings of run-off from pine forests into Deception

Bay, as a result of hydrological impacts associated with clear-felling.


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Global Implications

The combination of factors required for blooms ofLyngbya majuscula to occur is

specific: high concentrations of iron and phosphorus in either the sediment or water

column, dissolved organics in water column, warm waters and shallow seagrass beds. Itis hypothesized that increases in dissolved organics in the water column has provided the

missing link for enabling the bio-availability of the iron and phosphorus present.

Similarly, other blooms of cyanobacteria have been definitively linked with terrestrial

organics providing a source of bioavailable iron (Emmenegger et al. 1998). OtherL.

majusculabloom areas in the world may potentially have similar organic sources.

Bamboo and sword-grass trash is seasonally flushed into coastal waters of Guam during

the summer months of theL. majusculablooms (Matson 1991) although the link has not

been specifically drawn. The recent seasonal blooms ofL. majusculain Florida (USA)

are in the proximity of large freshwaterMelaleucaswamps which yield similar dark

stained waters to those observed in this study (Burns pers. comm.). Red tides

(dinoflagellate blooms) in Florida have also been linked with dissolved organics in the

water column (Ingle & Martin 1971).

It has been hypothesised that the greenhouse effect may be causing elevated primary

productivity in forests, which in turn is driving long-term trends of increasing dissolved

organic carbon and subsequent increases of water colour in natural water bodies

(Forsberg 1992, Doering et al. 1994). Based on this, in the coming decades coastal

waters may become warmer, more coloured and high in soluble complexed iron,

providing a hospitable environment for cyanobacteria. However, in some cases long-

term trends indicate dissolved organic carbon inputs into the coastal marine system are

decreasing. Urbanisation of catchments and associated deforestation has reduced forest

derived organic matter loadings (Kawaguchi et al. 1997, Matsunaga et al. 1999). The

resulting reduction in iron availability caused significant changes in the marine floral

ecosystem in both studies. These studies were conducted in catchments that had been

urbanized for some time. In contrast, the present study has focused on the short-term

elevation of organic matter loadings and elevated iron availability following

deforestation. Eventually the Pumicestone catchment may be more urbanized, which will

potentially result in a reduction in the bio-available iron, with further, yet unknown


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impacts on the marine system. Irrespective of the long-term trends in organic carbon

loadings, it is apparent that forests provide a critical function in regulating iron

availability in coastal waters. Anthropogenic manipulation of coastal forests can upset

the iron balance and, in turn, impact on the ecological integrity of the marine system.

TheLyngbya majusculablooms in this study provide an example of this. Based on thisrelationship between catchments and iron dynamics within the associated estuary,

Kawaguchi et al. (1994) have proposed bio-available iron as an indicator of upstream

catchment health.

Conclusions

It is concluded by this study that the changes in catchment land use can increase the

terrestrial nutrient input into coastal marine systems, altering water chemistry and in turn

leading to subsequent impacts on ecological integrity (e.g. formation of nuisance

cyanobacterial blooms). The results of this study clearly show that pine forest soils are

distinct from the other soils in most of the parameters assessed. The pine soils had higher

organic carbon content, high phosphorus concentration, high soluble iron, low pH, and

causedLyngbya majusculato have elevated photosynthetic capacity and high

phycoerythrin concentrations. Specifically, iron and phosphorus concentrations were

correlated with photosynthetic increases. Dissolved organic carbon within the forested

extracts altered light quality that theL. majusculareceived. Due to this altered light

spectrum, a shift in the relative proportion of photosynthetic pigments present occurred,

with a shift from chlorophyll ato phycoerythrin. It is likely that this physiological

plasticity in response to environmental parameters, exhibited byL. majuscula, offers a

selective advantage over other marine flora and enables the rapid growth to bloom

proportions seen in the region.

Hydrological changes, associated with pine forest clear-felling, increase the flux of

organics into surrounding waters. Thus, the elevated growth ofLyngbya majusculain

response to pine forest extracts is potentially exacerbated by more of these compounds

entering the bloom site. The conclusions drawn by this study have direct management

implications for potentially reducing the role terrestrial inputs have in stimulation ofL.

majusculablooms within Deception Bay. Management authorities often consider


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terrestrial and marine systems separately. This study has clearly shown but a few of the

important links, which exist between these systems. These links demonstrate that

terrestrial and marine systems are co-dependant. For the maintenance of ecological

integrity of either system, management must be considered on a holistic basis.

Notes on Methodo logy

Data from further studies using this methodology has been omitted from this report as the timing

of the bioassays caused discrepancies in the results. The data within this report is based on

bioassays conducted during the peak of the bloom (Jan/Feb) when the L. majuscula is

presumably at a physiological optimum. Bioassays conducted in the following months of the

bloom decline showed few significant responses to a large array of treatments. This observation

may lend weight to the argument that bloom decline is virally mediated (Hewson et al 2001),

rather than being a direct physiological response to environmental parameters such as light,

temperature and nutrients. Thus, recommendations for future use of this methodology are that

incubations using a seasonally blooming organism are conducted during the peak bloom period.

Acknowledgments

This research is the result of inputs from a team of people who have taken interest from the first

brainstorming session to the last correction in this thesis. Thanks to Judy ONeil for all her help

during the endless time in the lab and field. Bill Dennison provided much of the guidance and

insight to make this project possible from the outset. Thanks also to Phil Moody and David Waite

who guided me (an ecologist) through difficulties with soil science and iron chemistry respectively.Although easily convinced, Dan Wruck did the impossible and temporarily relocated his nutrient

analysis lab to our island research station to provide instant analysis. Thanks also to Alan

Goldizen, Andrew Watkinson and all the MarBot crew for lending a hand whenever needed.


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