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UGA MARS 3450 - 4 - Shallow water ecosystems

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Shallow Water HabitatsMARS 3450 3 October 2103Subtidal environmentsIntertidal environmentsNomenclatureSupra-littoral or splash zoneLight penetration is reduced in coastal watersTurbidity – suspended sedimentProducticity -> high phyto standing cropCDOM – Colored Dissolved Organic MatterNybakken Figure 1.25, p 37Supralittoral/Splash ZoneLittoral ZoneIntertidal ZoneLittoral ZoneIntertidal ZoneLittoral ZoneIntertidal ZoneSubtidal orSublittoralZoneTide poolLife at the Edgewww.waikato.ac.nz/wfass/e-reflections/2009/01/the-importance-of-estuaries-fo.shtmlLife at the EdgeAdvantagesFood high biomass and productivitywater movementShelter (something to hide under)predatorssunProblemsFoodYou ARE the foodGetting pounded by wavesShelterCompetition is fierceExtreme environmental conditionsTemperatureSalinityExposed ShelteredSolid RockyIntertidalPilings, sea walls, rocks, beerbottles, other organismsSediment Beach Mudflatatimesblogs.latimes.comGeneral Characteristics of Coastal Habitats1. Near humans (who have had a significant effect on coastal zones world-wide)General Characteristics of Coastal Habitats1. Near humans2. Highly productiveNutrients in Stratified Coastal WaterWater MovementMore Nutrients AddedGeneral Characteristics of Coastal Habitats1. Near humans2. Highly productive3. ShallowPresence of a BottomPhytoplankton GrowthBenthic Plant GrowthNutrient SupplyCritical Depth = Compensation DepthBenthic plants don’t circulate through the water columnRegenerationBut grazing is high, too!Classification of Benthic Organisms MacrofaunaAnimals > 0.5 mm1. Where they live:infaunaepibenthosBenthic Organisms - Macrofauna1. Where they live2. How they feedSuspension feedersChaetopterusSemibalanusbivalveSerpulaDeposit feedersHobsonia Yoldia MacomaPectinaria Corophium ArenicolaBenthic Organisms - Macrofauna1. Where they live2. How they feed3. What they eatHerbivoresTonicellaParrot fishArbaciaNereisCarnivoresNucella CuspidariaCallinectesGlyceraHaematousBenthic Organisms - Meiofauna“Meio-” = “Middle”, between Macro- and Micro-Animals < 0.5 mm (most are infauna most of the time)Characteristics of Meiofauna1. Vermiform shape (flattened, elongated)2. Reduced morphological complexity 3. Most adhere to particles 4. Adaptations to orient up and down5. Oxygen/Sulfide tolerances6. Vertically migrate7. Reinforced body walls (scales, heavy cuticles)8. Direct development (no planktonic stage for most)9. Some deposit feeders, some carnivores, no suspension feedersExamples of Meiofaunapolychaete copepod gastrotrich hydroid gastropodPhylum Ciliophora (Ciliates)Lots of these – important predators on bacteria, small eukaryotesPhylum Nematoda(lots of these)Phylum Platyhelminthes(flatworms)Phylum Annelida; Class PolychaetaPhylum Arthropoda; Class CrustaceaPhylum: Tardigrada Kinorhyncha GastrotrichsPhylum MolluscaEchinodermataPhylum CnidariaPhylum BryozoaOxygenNo Oxygen/Sulfidic1-5 mmAdaptations•Alternate (anaerobic) metabolism•Sulfide resistance•Migration•Leave sedimentDayNightNightSediment surfaceoxyclineConnections between meiofauna and other food websSeagrass Ecosystems•Seagrasses are true plants (Kingdom: Plantae)•Roots for anchoring and nutrient absorption•~50 species•Thin, strap-like leaves•Dense roots•Thick rhizomes(Nybakken 2001)Up to 4000 blades per m2•Subtidal (exceptions in mild climates; Oregon coast)•Lighted bottom (usually to 3-5 m; maximum = 60 m)•Sandy sediments (typically)Roots can penetrateRocky substrate not necessary•More protected areas than kelpWhere are seagrass beds found?ZosteraPhyllospadixZostera:temperate, eastern N. America; “eelgrass”Thalassia:tropical, Florida and Caribbean; “turtlegrass”Geographic Distribution(Levinton 2001)Bare sand SeaweedsHalodulegrassSyringodiumgrassThalassiagrassTurbulentresuspensionSediment stabilizationNutrient immobilizationOrganic matterSediment nutrientsSediment depositionNutrient regeneration•Important in colonization of bare sediments•Can spread by rhizomes to new areas•Can also reproduce sexually (inconspicuous flowers)•Macroalgae often arrive first and stabilize sediments,add nutrientsTIMENutrients lost Nutrients retainedColonization(Levinton 2001)•Thousands of shoots per m2•Water currents reduced•Capture sediment, stabilize sand•Encourages settlement of larvaeSoda straw experiment: moderate stem density reduces flow and distributes larval settlementStabilizationWater flowNo stemsModerate stem densityDense stems(Nybakken 2001)•Reduced water movement imports less O2•Build-up of organic matter in sediments from detritus•High bacterial decomposition activity•Result in anaerobic sedimentsLow Oxygen Content in Seagrass SedimentsHigh nutrient content in sedimentsBut P-limitedBut a fine balance: must keep enough O2to keep roots healthy, productivity highBut a fine balance: must keep enough O2to keep roots healthy, productivity highPrimary Production in Marine EcosystemsSystem gC/m2/y apples/m2/yOpen ocean <100 1Benthic deep sea* 0 0Coastal upwelling 300 6Kelp Systems 1300 26Tropical forests 1200 24Seagrass beds 800 16*doesn’t include vents and seepsGrowth rates up to 1 cm per day(Castro & Huber 2003)PhotosyntheticSpecialized larvae that recruit specifically to seagrasses(Atlantic bay scallop)Epiphytes Specialized forSeagrassesHeterotrophicNPNPNPFew animals graze directly!Protected by chemical compounds?10%?(Castro & Huber 2003)Seagrass Food WebMicrobesWhat happens to seagrass productivity?(Nybakken 2001)Export•As detritus: POC and DOC•As living tissue/fecal material from vertebratesTemperate seagrass system1930s: •Zosteranearly collapsed in Atlantic (except Mediterranean)•Associated animals also (such as bay scallop)•Commercial shellfish effects, ecological effects•Soft sediments eroded away•Recovery in the 1950sCause?•Perhaps a protistan pathogen•Perhaps increased fishing pressure (less epiphyte grazing means less light to seagrasses)Seagrass Community Declines1991:•Similar decline in Florida bay•Disease? •Eutrophication?•Temperature?•Chronically low O21960s:•Chesapeake bay declines•Due to disease?•Due to eutrophication and erosion?stimulates epiphytes blocks photosynthesisSeagrass Community DeclinesSubmerged aquatic vegetationFew hurricanes, reduced manatee and turtle feeding?(Heck et al. 2000)Due to Eutrophication?nutrientspinfish•Thalassia beds•Elevated N by 4-8 fold•Increased fish abundance•Will increased N lead todecreased


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