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BENTHOS BENTHOS: DEFINITIONS – Epifauna: live on or are associated with the benthic surface – Infauna: live within the substrate – Microfauna: animals <0.1 mm in size (e.g. protozoa/bacteria) – Meiofauna: animals <0.5 mm in size: “interstitial” (e.g. nematodes, sm. amphipods) – Macrofauna: animals > 0.5 mm in size: most familiar kinds of animals (crabs, shrimp, starfish and most mollusks) Abiotic Factors Affecting Benthos (to 200 m depth)) • Wave action: influence distribution of sediments and physically affect animals • Sediments: vary according to wave action (particle size sorting): terrigenous and marine origin (“allochthonous” and “autochthonous”): fine clays go to deeps • Salinity and temperature: FW influences; more thermal variability Distribution and biomass of benthos The Intertidal: Where the Benthos is Most Abundant • Biomass in intertidal= 10X that of 200 m depth and several thousand that of abyss! • Not without a cost: wave shock; desiccation; cold; osmotic issues; and land predators. But at high tide: plenty of O2; nutrients; light; and wastes washed away. • More relief and habitat diversity= more species diversity Reproduction and Dispersal • Broadcast spawning vs. brooding- varying amounts of energy invested, and value of dispersal • Where to settle? 1) chemical attractants: settle near your own kind 2) bottom types: settle in appropriate substrates PATTERNS OF DIVERSITY WITH DEPTH Where the food comes from Effects of predator exclusion on the abundance of macrofaunal molluscs, worm and crustaceans General results: 1) cages have up to 500 x density 2) more infaunal spp. in cages 3) no dominance by any single species Soft Sediment Communities • Types of soft-bottom habitats • Role of disturbance in regulating community structure • Effects of predation, competition and facilitation Submarine canyo Latitudinal Diffs. Temp. = sand Tropic. = mud Polar. = Gravel (Arctic w/ riverine mud) Deep seafloor Shallow water/Shelf Sandy shores/beaches Muddy shores/bays, estuaries, and lagoons Nearshore benthic habitats (0-200 m) Meiofauna (few mm) Benthic diatoms Harpacticoid copepods Foraminiferans Macrofauna (mm-cm) polychaete worms crustaceans Macrofauna (mm-cm) pycnogonids brittle stars heart urchins bivalves High biodiversity that varies with depth, sediment type and biotic factors Infaunal community “Patchiness” is the rule 1. Biotic interactions: predation, competition, & facilitation 2. Physical factors: disturbance (biotic, physical, and anthropogenic) Community patterns and structure Temperate/tropical Polar Megafauna (cm-m) grey whales Predators have a big effect on community composition walrus Caging Studies Direct and indirect effects of predation in soft-sediment food webs Life-history groups Important classification for understanding effects of disturbance Succession Capitella captitata BIOTURBATION Upogebia- another burrowing shrimp Upogebia BURROW fecal strands from polychaetes Burrows of Callianassa BURROWING SHRIMP Callianassa MORE BIOTURBATORS Harpacticoid copepod Oligochaete: Paranais Burrowing holothurian Polychaete: Nereis The lugworm (Arenicola) and its burrow/fecal castings Gastropod: Hydrobia Gastropod 2: Ilyanassa Sediment modifiers Ammensalism/mutualism Facilitation Competition can be important in soft-sediment communities •Competition in a 3-d environment: rarely for space • Competition usually for food with big effects on growth, reproduction, and survival. Density-dependence common • Competition has a big effect on community structuredepth distribution, population distribution, abundance, and dynamics The intermediate disturbance hypothesis Would you expect the intermediate disturbance hypothesis to explain diversity patterns in soft sediments? Types and scales of disturbances in soft-sediments Disturbance caused by eutrophication Iceberg scour disturbance On frequently scoured seafloor, what functional groups would you expect? Re-colonization • Different mechanisms: • Vegetative regrowth of survivors • Recruitment from propagules (including spore and seed bank) • Influence of patch characteristics: • Size and shape • Substrate characteristics (e.g. rock or sediment types, topographic complexity, biogenic structures) • Patch location (environmental conditions and proximity to propagule sources) • Timing of patch creation (availability of propagules and differences in conditions) PHYSICAL DISTURBANCES Agent of disturbance Direct impacts on organisms and Substrate Habitat or assemblages effected Waves and currents Sessile organisms detached or broken Mobile animals displaced, injured, or killed Substrate overturned Sediment eroded Most, declines with depth Water-borne material (sediment, logs, rocks) Organisms abraded, buried, crushed or detached Most Ice Organisms abraded, detached Sediment and organisms excavated and displaced Rocky intertidal and subtidal, Soft sediment, Seagrass beds, Salt mashes (high lat) PHYSICAL DISTURBANCES Agent of disturbance Direct impacts on organisms and Substrate Habitat or assemblages effected Extended aerial exposure Organisms injured or killed by desiccation, heat, UV Rocky intertidal Coral reefs Seagrass beds Temperature extremes Organisms injured or killed by heat or cold. Bleaching Tide pools, Kelp forests, Coral reefs Salinity stress and freshwater flooding Organisms injured or killed by osmotic stress Rocky intertidal, Salt marsh, Coral reef, Mangrove, Soft sediment Anoxia Organisms injured or killed by metabolic stress Soft sediment, estuaries, semienclosed seas PHYSICAL DISTURBANCES Agent of disturbance Direct impacts on organisms and Substrate Habitat or assemblages effected Landslides, tectonic events Organisms abraded, crushed, displaced, or smothered Rocky intertidal and subtidal, Soft sediment, slope and rise,vents Lava flow, volcanic ash Organisms injured or killed by lava, smothered by ash Rocky intertidal and subtidal, Seagrass beds, Coral reefs, vents Fire, lightening strikes, Organisms injured or killed by heat Salt marsh, Mangrove Meteorite impacts Direct impact and climate change Global (mass extinctions) BIOLOGICAL DISTURBANCES Agent of disturbance Direct impacts on organisms and Substrate Habitat or assemblages effected Accumulation of plant or animal material (wrack and carcasses) Organisms smothered, buried and shaded, chemistry Salt marsh, Seagrass beds, Soft sediment Algal whiplash Organisms abraded, recruits vulnerable Rocky intertidal and subtidal Bioturbation Soft sediment, Organisms buried, sediment load interferes with feeding Seagrass beds Sediment excavation by predators Organisms displaced, uprooted, and buried Accumulation of debris Soft sediments Seagrass beds BIOLOGICAL DISTURBANCES Habitat or assemblages effected Agent of disturbance Direct impacts on organisms and Substrate Haul out, trampling Organisms smothered, buried, Rocky intertidal smashed Red tide Organisms suffocated and poisoned Soft sediment, coastal environments Anthropogenic disturbances in soft sediment habitats Oil spills Exxon-Valdez oil spill •Bleigh Reef in NPWS Ecosystem level impacts •42 million L of oil •1990 km of coastline and 750 km southward Prince William Sound, AK on 24 March 1989 •14 years of intensive study Ecological impacts of the EVOS •New understanding of long-term effects and recovery processes. Ecosystem-based toxicology •Before: short-term impact assessments and lab studies of toxic effects •First real ecosystem impact study General conclusions: 1) Oil persisted beyond a decade in surprising amounts and toxic forms because of the presence of soft-sediments 2) Oil significantly bioavailable to induce chronic biological exposure 3) Longterm effects at population level Ecological impacts of the EVOS 3 major pathways of exposure & induction: •Acute exposure to oil during spill and subsequent negative health effects •Chronic persistence of oil, bio-exposure, and population impacts to species closely associated with shallow sediments •Indirect effects related to predator-prey relationships, loss of habitat Acute effects of spill •Oil in fur, feathers, and ingested •1000-2800 sea otters •~250,000 seabirds •302 harbor seals •Mass mortality of macroalgae, benthic invertebrates on shore from a combination toxicity, smothering, and physical displacement caused by high pressure clean-up Persistence of oil •40-45% oil grounded in 1989 on 787 km of PWS beaches •7-11% contaminated 1203 km of Gulf of AK coastline •2% remained on beaches after 3.5 yrs (-0.87 per yr) •Rates of dispersion and degradation diminished through time •Suppressed by physical barriers to disturbance, oxygenation and photolysis •Oil trapped in sediments and mussel beds Effects of chronic exposure •Chronic exposure of sediment affiliated species •Fish embryos exposed to partially weathered oil •Multi-ringed PAHs toxic to pink salmon eggs at 1 ppb when exposed for months •Toxic to herring eggs when exposed for 16 days •Reduced salmon and herring reproduction in many areas Effects of chronic exposure •Led to death from compromised health, growth, or reproduction •Lower growth rates of salmon = reduced survival •Abnormal growth in herring and salmon caused by endocrine disruptors = less fat Cascades of indirect effects •Two most important types of cascades •Trophic cascades in which predators reduce abundance of their prey which releases the preys food species from control •Provision of biogenic habitat by organisms that serve as or creates important physical structure in environment •Current Risk Assessment models used for projecting biological injury to marine communities ignore indirect effects Four groups of dominant macrofauna in soft bottoms • Class Polychaeta: most numerous: tube-building and burrowing • Subphylum Crustacea: ostracods, amphipods, isopods, tanaids, mysids, small decapods • Phylum Mollusca: burrowing bivalves and scaphopods, gastropods at surface • Phylum Echinodermata: brittle stars, heart urchins, sand dollars, sea cukes Soft- and hard-bottom benthic communities • Soft: little ‘relief’: ripple marks, worm tubes, fecal mounds: some differences in sediment grain size: fewer inds. And infauna and more epifauna in sand: more individuals in mud and most are deposit feeders • Hard: more ‘relief” and more habitat diversity: increase in suspension feeders Feeding strategies • Deposit feeders: feed on organically enriched sediments: continuous “reworking” of sediments to extract nutrients: analogous to earthworms: can live in very fine sediments • Suspension feeders: filtering devices or mucus nets collect detritus or plankton: need coarser sediments or hard bottom • Grazers/predators/scavengers Deposit Feeders Sponge Bivalve Amphipod Bryozoan Hydroid Suspension feeders Polychaete Tunicate Brittlestar Barnacle Anemone PARALLEL BOTTOM COMMUNITIES FUNCTIONAL GROUPS (or: bioturbators) FEEDING IN AN INFAUNAL CUCUMBER PREDATORS OF BENTHOS CAGE STUDIES COMPETITION FOR SPACE LIFE IN THE MUDS: A COMPLEX SITUATION COMMUNITY CHANGES: STORM INDUCED SEASONAL POPULATION CHANGE LONGER-TERM OSCILLATIONS IN ANOTHER AMPHIPOD Biomass of benthos in relation to distance from coast and depth RECOVERY OF BENTHIC COMMUNITY FOLLOWING DEFAUNATION BY RED TIDE