Sediments Types of substrates: hard, soft Types of sediments Clastics: abiotic Carbonates: abiotic, biotic Sediment distribution in the oceans Importance of sediments to organisms, ecosystems, and chemistry

Substrate types Hard bottoms: rocks, hardgrounds, other organisms, and artifical substrates Energy: waves, currents Epibiosis

Substrate types Soft bottoms: muds, sands, gravels semi-hard to soupy Energy determines grain size Infauna and epifauna Bioturbation Oxygenation and anoxia

Sediment properties Texture = size assortment Maturity = clay amount, sorting, roundness

Clastic (lithogenous) sediments Pebbles, sand, silt, clay Abiotic, but can have biotic help in weathering Weathered rocks (chemical and physical) The Rock Cycle

Sediment Deposition Particles into drainage basins then into oceans Particle size is determined by energy of transport FW input, storm transport Exception: ice Distance from shore: deposition determined by amount of input, size of particles, energy

Carbonate sediments Calcium carbonate: CaCO3: formation and dissolution CaCO 3 + H 2 O + CO 2 ↔ Ca HCO3 - Calcium carbonate + water + carbon dioxide ↔ calcium + bicarbonate

Carbonate sediments Abiotic precipitation (rare) Biotic precipitation: shells, etc. Soft substrates, grain types: peloids, pellets Ooid sands Shell debris Halimeda

Carbonate sediments Weathering: algal borings breakagedissolution Role of CO2 and anthropogenic effects

Carbonate sediments Cambrian explosion: 535 MY

Ocean sediment distribution Tropics: Carbonate, clastics on shelf Polar regions: Cold carbonates, ice float and boulder drops DepthEnergy Proximity to land Chemistry

Shallow sediments Variable sed rates Relict sediments Turbidites Glacial depositsStromatolitesReefs

Deep sediments Low sed rates Abyssal clay Oozes Organic detritus Dust Phosphate nodules

Sediments and Organisms Benthos versus Nekton, Plankton Soupy to firm bed: different organisms Sessile versus vagile Epifauna, infauna

Sediments and Organisms Organisms modify environment BioturbationReefs

Sediments and Organisms Feeding stragegies: filter feeding, filter feeding, deposit feeding, scavenging, predation scavenging, predation

Sediments and Organisms Larvae, adults, and recruitment Many benthic organisms have planktic larval stage Settlement and metamorphosis cues

Sediments and Ecosystems Stratified sediments versus bioturbation Grain size effects Energy effects

Sediments and Ecosystems Microbial loop; detrital food chain and nutrient recycling Important part of ecosystem in shallow water Benthic singe-celled algae

Sediments and Ecosystems Succession Environmental perturbation Predictable: seasonality (T, precipitation) Unpredictable: large storms, anthropogenic effects

Sediments and Chemistry Nutrient recycling: microbial loop, algae Nutrient, carbon sink Sediments buffered from salinity changes Anoxia at depth Toxin filter Pollution trap