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Lecture Benthic Ecology
Salt marshes are sediment-covered shores
• Salt marshes and estuaries (regions where freshwater and saltwater meet) are highly productive benthic habitats
• Much of this productivity comes from sea grasses, mangroves and other vascular plants
• Salt marshes form in estuaries and are characterized by specialized plants capable of surviving in (and then out of) salt water
Salt marshes: Home Sweet Home
• Salt marshes – via their specialized plants –form protective barriers against erosion, and promote new land formation as plant roots trap sediments on each tidal cycle, and filter out excess nutrients and pollutants
• Salt marshes also provide protective habitat for larval fish species, and provide food and shelter for migratory waterfowl; marsh plants also form the base of the food web via decay
Salt Marshes are Vital Habitats!
http://en.wikipedia.org/wiki/File:Bride-Brook-Salt-Marsh-s.jpg
Classification
Five kingdom system:
Monera Protista FungiPlantae Animalia
Angiosperms Gymnosperms
Distribution: 12 genera of seagrasses (5 in the high latitude and 7 in the low latitude)
• True marine angiosperm• Evolved from shoreline Lillie-like plants~100
mya• Vascular plants reinvaded the seas 3 different
times (algae is nonvascular; i.e., no need for roots to transport water and nutrients)
• Can grow and reproduce while completely submerged under water
Halophila hawaiiana- only form of seagrass in Hawaii
Develop in:• intertidal and shallow subtidal
areas on sands and muds• marine inlets and bays • lagoons and channels, which are
sheltered from significant wave action
1. Help stabilize the sediment
2. Prevents resuspension of sediments in water (water is clearer)
3. Binds substratum, reduces turbidity, and reduces erosion
4. Sediment accumulation slows velocity of incoming water
5. Food for many organisms
6. Refuge for many organisms
Seagrass productivity is highly dependent on a number of factors:• salinity• water temperature• turbidity
This ecosystem is particularly sensitive to degradation due to:• agricultural pollution-run-off of
herbicides• industrial pollution• domestic pollution
Threats to Seagrass Beds
Coral Reef Communities
Hermatypic corals:• possess zooxanthellae• are reef builders
Light: Clear water Warm temperature: 18-32oCLow nutrientsLow productivity in water
Ahermatypic corals:• no zooxanthellae• rely on tentacular feeding• can live in aphotic zone
Cauliflower coral(Pocillopora meaandrina)
6 m
0 m
25 m
13 mLobe coral(Porites lobata)
Finger coral(Porites compressa)
Plate coral(Porites rus)
High light levelsModerate wave energy
Moderate light levelsOccasional storm wave energy
Low light levelsLow wave energy
Very low light, Primarily downwelling No wave energy
Coral Reef Communities
• Corals are animals (Cnidarians) related to anemones and jellyfish
• Most corals secrete hard skeletons of calcium carbonate and produce coral reefs
• An individual coral – known as a polyp – feeds by capturing and eating plankton that drift within reach of their tentacles
• Corals produce sexually and asexually
Hermatypic corals:• possess zooxanthellae• are reef builders
Light: Clear water Warm temperature: 18-32oCLow nutrientsLow productivity in water
Ahermatypic corals:• no zooxanthellae• rely on tentacular feeding• can live in aphotic zone
Coral Reef Communities
• Corals form symbiotic relationships with dinoflagellates, known as zooxanthellae
• Zooxanthellae receive nutrients and shelter from the coral, and photosynthesize, providing the coral with organic compounds
• Zooxanthellae provide corals (otherwise translucent) with their brilliant colors
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Coral reef distribution and diversity
Figure 15-18
Tropical coral reefs support large numbers of species
• Reef-building corals provide substrate for other organisms to attach and hide
• Corals also provide a source of food in otherwise weakly-productive regions
• Coral bleaching (the loss of the symbiotic zooxanthellae in response to environmental stress) may kill the coral, and have devastating impacts on the coral reef community
Coral Bleaching
www.cgrer.uiowa.edu/peoplecarmichael/atmos_course/ATMOS_PROJ_99/jlmichfin/main.html
Corals are stressed by environmental change
• A water temperature change of only 1°C above the normal summer high temperature for a few weeks leads to coral bleaching– Coral expels zooxanthellae or zooxanthellae expels
itself
• El Niño events can drive coral bleaching• May be reversible – corals can re-aquire new
zooxanthellae if the stress is not too severe
The deep-ocean floor
• Characteristics of the deep ocean:– Absence of sunlight– Temperatures around freezing– Average salinity– High dissolved oxygen– Extremely high pressure– Slow bottom currents (except abyssal storms)– Low food supply
© 2011 Pearson Education, Inc.
Deep Ocean Physical Environment
• Bathal, abyssal, hadal zones• Light absent below 1000 meters• Temperature usually between -1.8°C and
3°C• High oxygen• High pressure• Abyssal storms – affect bottom currents
© 2011 Pearson Education, Inc.
Deep Ocean Food Sources and Species Diversity
• No primary productivity• Only 1 – 3% of euphotic
food present• Special adaptations for
detecting food• Species diversity
equivalent to rain forest
Deep-sea hydrothermal vent biocommunities
• Found in deep water near black smokers along the mid-ocean ridge
• Do not rely on food from sunlit surface waters• Organisms include:
– Tube worms– Clams– Mussels– Crabs– Microbial mats
© 2011 Pearson Education, Inc.
Deep-Sea Hydrothermal Vent Biocommunities
• Discovery – Alvin in 1977
• Galapagos Rift in Pacific Ocean
• Water temperature 8–12°C (46–54°F)
• Chimney vents, hot acidic water – Black smokers
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Locations of Hydrothermal Vent Communities
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Chemosynthesis • Microscopic archaea – thrive on hydrogen sulfide
from vents– Manufacture sugar, carbon dioxide, and dissolved oxygen
• Base of hydrothermal vent food chain
© 2011 Pearson Education, Inc.
Hydrothermal Vent Species• Giant tubeworms• Giant clams• Giant mussels• Crabs• Microbial mats• Life supported by
chemosynthesis
Phylum Annelida 30
Family Siboglinidae• Defining characteristic
– Gut tissue forms an organ (trophosome) that becomes filled with chemosynthetic bacteria
– Segmentation confined to small rear portion of animal (the opisthosoma)
• Small intriguing class of tube dwelling worms found throughout the worlds oceans
All 120 species are marine and can be found in high concentrations on hydrothermal vents
Clade Siboglinidae (Phylum Pogonophora)
Ridgea spRiftia pachyptila
Giant tube worms (Vestimentifera)
Riftia pachyptila
trophosome
Phylum Annelida 33
Trophosome• The major organs (gonads
and trophosome) are found in the coelom
• The trophosome of all species contains closely packed bacteria and play a crucial role in nutrition
• The last segment is the opisthosoma, which has many segments and septa like polychaetes
Phylum Annelida 34
Chemosynthetic Bacteria
• The most interesting aspect of pogonophora is the lack of a digestive system– Bacteria in the
trophosome fix the chemicals leaving the vents
– The bacteria can occur at concentrations of 10 billion per gram of trophosome tissue
Figure 8.1 The effects of competition and predation on barnacle distribution in Scotland. Ci, intraspecific competition; C2, interspecific competition between Chthamalus an6 Balanus, D, desiccation; P, predation by Nucella, a predatory snail. The widths of the distribution bars indicate relative abundance; the widths of the mortality bars indicate relative importance of the factors concerned. Note that the upper limits of distribution for both species are determined by physical factors (i.e. tolerance to dessication). Snail predation andintraspecific competition for space are the major causes of mortality for Balanus, and both factors become increasingly important at lower tidal levels. For Chthamalus, the major cause of mortality of newly settled larvae is intraspecific competition for space with thefaster-growing Balanus. Few Chthamalus larvae settle below mean tide level, but those that do are eliminated by predation and interspecific competition.
When the top predator is removed, competition for space is intensified and, in this region, Mytilus californianusovergrows and outcompetes all other macrobenthos to take over the available space throughout most of the mid-intertidal zone. Pisaster is referred to as a keystone species
An idealized diagram of the distribution of freshwater, brackish-water, and marine animals relative to salinity. (Numbers of species given in relative units.)
The biomass on the sea floor tends to decrease with depth faster than it
does with distance from shore.• The benthic food chains largely depend upon
food from the surface which reaches the bottom.• Characteristics of the benthic organisms include:
year-round reproduction, smaller broods, slow growth, and longer life.
• Diversity of the benthos is greater than expected because the high predation rate prevents any group from dominating through competitive
13-2 Biology of the Open Ocean and the Deep Sea
• Four traits common to all abyssal depths are: perpetual darkness., low temperature, high hydrostatic pressure, and sparse food supply.
• Rate of bacterial decay is greatly reduced under high hydrostatic pressure.
• This means that organic material that settles onto the sea floor remains for a long time before it decays and is thus more likely to be consumed.
13-2 Biology of the Open Ocean and the Deep Sea