Saltmarshes

Saltmarshes

• Saltmarshes often found in upper reaches of an estuary (and elsewhere)

• Sand/Clay/Silt and/or organic materials• Minerogenic or organogenic marshes• Classification into: open coast marshes;

back-barrier marshes; estuarine-fringing marshes; embayment marshes; loch or fjord-head marshes

Saltmarshes

• Evidence of accretion (but also erosion)• Controlling Factors: sediment supply;

tidal regime; wind-wave climate; movement of relative sea level

• Tidal cycles, inundation, accretion• Saltmarsh ecosystems are sensitive to

changes in sea level and isostatic adjustments to the level of the land

Saltmarshes

• Tidal range and exposure• Submergence and emergence marsh• Low, middle and high marsh• Accreting salt marshes can gain height

and prograde (increase in seaward extent)

• Saltmarshes can build in height (vertical accretion) but can also suffer subsidence (compaction of sediments)

Saltmarshes

A salt marsh is "born" by the arrival of a seed or the rafting of a plant of the cord grass Spartina alterniflora. The grass spreads asexually by means of a subterranean rhizome system. The grass becomes dense and forms a baffle, which encourages the deposition of fine particulate sediment, including organic matter (salt marsh peat). This, in effect, causes a rise of the sediment surface and makes the habitat more terrestrial. As this happens, other somewhat less salt-tolerant grasses are able to invade. Eventually, this series of invasions and takeovers leads to a vertical zonation of grasses and a spread of the entire marsh system.

SAS = Spartina alterniflora - short form

SP = Spartina patens, the next higher grass species

Saltmarshes

• Topography of saltmarsh results from the interaction of the processes of deposition, erosion, and sediment consolidation

• Formation of Creeks and Salt Pans• Primary and Secondary Pans• Creek or Channel Pans• Microtopography

Saltmarshes

• Slope and presence of creeks and salt pans influences the distribution of animals and plants

• Zonation of vegetation (low, medium, high)• Number and distribution affected by

location in saltmarsh, but also local climate e.g precipitation as well as evapotranspiration

• Many species of plants and animals

Saltmarshes

Saltmarshes

Saltmarshes

Saltmarshes

• Flora: Salicornia and Sarcocorni (glassworts), Spartina (cord-grass), Juncus (rushes), Plantago (plantains), and Limomium (sea-lavendars) - grasses are often very common ( Spartina anglica, Puccinellia maritima, Festuca rubra, Agrostis stolonifera, Phragmites australis, Spartina alterniflora

Saltmarshes

• Developmental zonation• Many saltmarshes are very old - well

established• Zonation may be well established• Vegetation succession (organisms and

environment - Autogenic versus Allogenic factors)

• Varying nutrient, fluvial and groundwater fluxes between saltmarshes and estuaries

Saltmarshes

• Net importers / Net exporters of nutrients (nutrient flux)

• In maritime saltmarshes: tides influence sedimentation rates, ionic relationships, water regime, photosynthesis, and ability of seedlings to establish

Saltmarshes

• Animals:marine invertebrates, deposit feeders, burrowing worms, oligochaete and polychaete worms, crustaceans, ragworms, bivalve molluscs, gastropods, crabs, fish, insects, birds, rabbits

Saltmarshes• Facultative mutualisms between Spartina

alterniflora and the marsh mussel Geukensia demissa and between and fiddler crabs Uca pugax

• Fiddler crabs increase soil aeration• Mussels deposit nitrogenous

wastes • Spartina anglica - invades

intertidal flats rich in invertebrates and promotes reclamation

• In some places losing ground - oil pollution and accumulation of fine-grained sediment

Saltmarshes• Saltmarsh dynamics• Seasonal growth and dieback• Halophytes and Glycophytes• Seasonal biomass accumulation• Rainfall and salinity affects vegetation

cover/survival• Seasonal behaviour in animals e.g. birds• Impact of grazing on plants and succession• Biomass, productivity and energy flow• Algal productivity: creek sides, plant stems

Saltmarshes

• Spartina alterniflora marsh• Ecological processes involved in terms

of the overall carbon balance• Ecological processes in the water:

phytoplankton, filter feeding, particle feeding, microbial assimilation

• Ecological processes in the marsh sediments

• Tidal exchange for transport of organic matter

Sand Dunes

Sand Dunes

• Large supplies of sand moved onshore by wind

• Integrated beach-dune system• Deflation / Abrasion / Saltation / Surface

Creep• Sand dunes found around the World• Dynamic environment but can become fixed• Some are devoid of vegetation others are

not (phytogenic)

Sand Dunes

• Different classifications of dunes• Shape or form, orientation (parabolic,

transverse, longitudinal)• Characterised by spatial distribution of

sand, height, presence/absence of vegetation, topography

• Formation (and duration) dependent upon supply of sand, obstacles, rate of sand transport, wind direction/speed, changes

Sand Dunes

• Transect through dunes: sea, foreshore, strandline, backshore, embryo dunes, mobile (young or yellow dunes), (lower) unconsolidated dunes, consolidated (mature) grey dunes, and the maritime sward (dune heath) (also dune slacks)

• From sea to land: ground wind speed, influence of salt spray, soil pH and levels of soil calcium, and sodium diminish whilst….

Sand Dunes

• Extent of vegetation cover, amount of organic matter, number of plant and animal species and overall stability increase

• Exposure and shelter (from wind and salt water) determine the type and distribution of plants

• Landform, soil and water regime have an influence on the vegetation

• Over time soils develop: mineral versus organic material e.g. in dune slacks

Sand Dunes• Mobility of sand through erosion will determine

where the vegetation grows• Sand often has little in the way of nutrients• Limiting levels of nutrients: nitrogen, phosphorous

and potassium• Shell fragments provide calcium• As the proportion of organic matter increases so

the ability of the soil to retain moisture and nutrients rises

• Fixed rather than mobile dunes will have more soil development

Sand Dunes

• Soil processes active e.g. leaching will wash out nutrients in soils (lower in the profile or out of the ‘system’)

• Vegetation once established will contribute e.g. organic carbon

• Access to water via the water table• Also dew formation (water carried in air

from sea) provides valuable moisture for shallow rooted plants in sand dunes

Sand Dunes• Dune slacks (wet and dry)• Presence of water dependent upon water

table (also from dew and rainfall)• Provides water supply for plants• Also capillary water - accessed via deep

rooting systems• Availabilty of water determines distribution of

plants• Besides vascular plants also presence of non-

vascular such as mosses and lichens

Sand Dunes• Vegetation in dune systems is affected by

grazing e.g. by rabbits• Exposure of soil and sand

to erosion• Affects species structure

and diversity• Also effects of trampling• Large areas of dunes often covered in marram

grass (rhizome fragments and also seedlings)• Sand traps

Sand Dunes• Vegetation: Ammophila arenaria P (marram),

Elytrigia juncea P (sand couch-grass), Honckenya peploides P (sea sandwort), Cakile maritima A (sea rocket), Euphorbia paralias P (sea spurge), Salsola kali A (prickly saltwort) - annuals, biennials, perennials

• Also lichens and mosses• Animal populations e.g. birds, reptiles

(lizards (Lacerta agilis; Lacerta vivipara) and snakes (Coronella austriaca), and insects

Sand Dunes

Sand Dunes• Stabilizing role of marram grass• Dieback of marram can be due

to poor aeration, mineral content deficiency, competition for nutrients, toxicity, natural senescence

• Soil biota (mycorrhizal fungi and nematodes) play a major role in vigour of marram

• Areas of deflation are ideal for the settlement of species such as meadow red fescue - source of water

• In some dune systems shrubs e.g. Sands of Forvie and forest e.g. Culbin Sands

Sand Dunes

Sand Dunes

www-biol.paisley.ac.uk/bioref/ Habitats/Dunes2.htm

http://www.geographyinaction.co.uk/Magilligan/Mag_intro.html

Sand Dunes• Influence of size and also humans

(management, disease)• Affects biodiversity• Machair – April 20th