PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17BENTHOS•Substrate determines distribution:Macro - > or equal to 0.5 mm Meio - < 0.5 mm (selected for uniform body shape)Micro - < 0.1 mm• Soft-Sed. Parameters-• grain size analysis:<62 mm (silt-clay fraction); % clay <4 mmBiogenic Sorting:• organisms ingesting sediment prefer to consume small particles - transfer to surface• maldanid polychaete - Clymenella torquata ingests <1 mm (conveyor-belt feeders)• bioturbation can affect depth of redox potential discontinuity (RPD)Biotic Effects on Chemical Properties:• Rhoads, 19741) rate of exchange of dissolved or adsorbed ions, compounds, and gases across sed/water interface2) vertical gradients - pH, Eh, pO2, depth RPD3) cycles of C, N, P, S -Fe4) transfer of reduced compounds from below the RPD to surface-oxygenated sedimentsAller &Yingst, 1975 - burrow walls had brown-orange oxygenated halo a few mm surrounded by black (Fe-sulfides) sedimentZobell, 1938 - pellets enriched in microbiotaHylleberg, 1975 - irrigation stimulates growth of microorganismsBiological Influences on Mass Properties of Sediments:• pseudofeces• feces both produced in upper 2-5cm Sediment Water and Oxygen Content:• flocculent zone (Sanders, 1960)• pelletized layers• Increase of water content alters mass properties of the sediment and greatly reduces the effort needed for burrowing to penetrate the substratum• High water content – thixotropic - speed of burrowingProperties of the Sed-Water Interface and Turbidity of Overlying Water:• Effects of burrowers on laminar flow or turbulent flow - and sediment resuspension• Topography – Callianassa spp.– burrowing shrimp, can go down to 2-3 m.• Molpadia oolitica - holothurian - permits colonization by several spp. of suspension-feeding, tube-dwelling polychaetes (Rhoads & Young, 1971; Rhoads, 1974)• Ingestion rates of individual deposit-feeders - pop. effects - reworking of sediments• Deposit-feeding bivalve Nucula annulata:• rework the annually deposited sediment 1-5 times/d-1 - thus, sediments are often pelletized • Suspension-feeders - enrich sediments with fecal pellets – populations of Cardium edule biodeposits 100,000 metric tons of suspended matter/yr -1 in Dutch Wadden Sea• Particulate Organic Matter (POM) in sediments• Detritus - inputs• In pelagic realm 60-90% of the 1° production is consumed by herbivores * the remaining goes into sediments• Much of the 1° production of benthic seaweeds, kelp forests, sea grasses, mangroves, and marsh grasses - is thought to not be consumed – recent work challenges this theory• The larger majority of benthic primary production (5000-1000 gC m-2yr -1) enters the food chain as detritus• N. Atlantic kelp - Laminaria longicruris• Mann, 1972 - dominant inputs to benthos, much of it is consumed• In contrast Zostera marina decays more slowly - not so important as a benthic food source• St. Margarets Bay, Nova Scotia - 15% of the seaweed production reaches the sediment as deposited organic detritus• Georgia - 90% of detritus in estuarine creeks is of Spartina spp. originAdaptation of Benthic Organisms:Epibenthos - barnacles, seaweeds, oysters, serpulid polychaetes1) Adoption of short squat profile to minimize exposure to shear stress (i.e., anemones)2) Hiding in holes (cryptic)3) Stout rigid support structures (thick byssal threads) (i.e., Mytilus californianus) 4) extensibility• Metridium senile - tall• Anthopleura xanthogrammica - short •Acropora palamata - strong• Montastrea annularis - weak and massive• Sea Fans - Gorgonia - prefered orientation to the currentSwimmers:• Octopus - compressible mantle cavity• Pecten• Polychaetes - sinusoidal wavesInfauna:• In order to penetrate soft sediments, infauna must exert a forward thrust within the sediment while maintaining points against which force can be exerted• soft-bodied - form a penetration anchor, then a terminal anchor• lugworm - Arenicola - proboscis exerted Abarenicola• streamlined bivalves in sand – razor clam • Ensis directus - rapid borrower• broad-shaped bivalves • Mya arenaria• Many bivalves squirt water with siphons to facilitate burrowing• Many infaunal animals make permanent burrows• Maldanid - ice-cream cone worm, Pectinaria - even-sized sand grains• Many find sediment-dwelling infauna do not maintain vertical burrows and burrow laterally• Yoldia limatula & Nucula - protobranch bivalves• Nephthys incisa - polychaetes - responsible for fluidized nature of