Benthic Pelagic Coupling and Deep Sea Energetics Refer to Gage J Ch 11 in Ecosystems of the Deep Oceans P Tyler ed 2003 Thanks to Ken Smith for many slides Food inputs and fluxes Aspects of Coupling Seasonality of production and OM deposition Particle dynamics at the boundary layer Structure of Deep sea Food webs Benthic responses SCOC C supply and demand Body size feeding types Lg organic falls Scavenging 1 Solar Energy Air Sea Interface Primary Consumers Secondary Consumers Tertiary Consumers Primary Producers Food Energy Benthic Boundary Layer Sediment Water Interface What is the benthic boundary layer W The layer of water immediately above the bottom that is mixed by turbulent shear with the bottom Heterotrophic system Allochthonous OM derived from the euphotic zone and nearshore neritic and terrestrial inputs 2 Early Observations Supply of dead surface animals to the seabed Challenger previous Fast sinking gelatinous plankton supplied to the sea floor seasonal Moseley 1880 Feeding types in the deep sea Sokolova 1959 Low degradation rates ALVIN LUNCH 1968 Key Transitional Observations Discovery of seasonal peaks in flux of organic particles into sediment traps at depth Deuser and Ross 1980 3200 m 6 wk lag from surface Deuser et al 1981 3 Seabed photographs showing massive accumulations of phytodetritus on the abyssal sea floor Billett et al 1983 Rapid microbial response by barophilic bacteria to freshly deposited phytodetritus Lochte and Turley 1988 http pcwww liv ac uk earth crozet images Fig1 jpg Responses to Food Falls challenging the paradigm of constancy Scavengers attack dead animal falls Isaacs and Schwartzlose 1975 Hagfish lyssianasid amphipods isotopods brittle stars 4 Boring bivalves attack wood Turner 1973 Seasonal variability in reproduction recruitment growth Tyler et al 1982 Gage and Tyler 1991 Paradigm Shift benthic pelagic coupling is highly dynamic and variable Forms of OM transported to the BBL Passive detrital rain Remains of plankton fecal pellets moults Plant debris and animal carcasses Small light particles bacteria etc remain suspended indefinitely Dissolved organic matter DOM derived from POM usually refractory In situ production chemosynthetic 5 Newly appreciated role for flow Resuspension Lateral transport Episodic large scale events slides turbidity flows triggered by earthquakes Flow mediates the fate of sinking OM Mechanisms of Transport 1 Passive Sinking 10 escapes euphotic zone Sinking at rates of 20 1000 m day Reflect surface production seen in chloroplastic equivalents in the sediments Only 1 3 of surface primary production reaches the seabed Deuser 1986 Most is utilized by midwater organisms 3 4 of OM is recycled in the upper 500 1000 m Many particles carry their own microbial decomposers Organic content of particles and size becomes more variable with depth 6 1a Event Sinking blooms that overwhelm grazers 1b Particle aggregation e g marine snow particles greater than 100 microns may be many cm across sinking rates of 1 368 m d Bound by sticky mucus exudates polychaccharides secreted by plankton bacteria contains clay particles bodies of gelatinous zooplankton Fecal Pellets One form of aggregated particles Copepod pellets sink at 153 m d Jelly and pteropod pellets can sink at rates up to 2100 m day Carbonate and silicate inorg act as ballast Greater nutritive value than fine particles because they sink quickly and arrive less degraded 7 2 Ladder of Vertical Migration Vinogradov and Tseitlin 1983 Vertical migrations of zooplankton and micronekton transport material in guts 5 of mass flux to depth Lampitt et al 1990 Ascension of demersal species e g shrimp hake orange roughy to feed in the midwater Benthopelagic scavengers mainly redistribute food Vertical Migration ONTOGENETIC squid shrimp fish ostracods euphausids chaetognaths Larvae near surface adults live deeper Yields spatial separation that reduces competition SEASONAL in NE Atlatic Calanus finmarchicus overwinters at 1000 m no feeding rises to the surface in spring Neocalanus plumchris overwinters at 100 250 m in the N Pacific Upwelling drives seasonality Deep dormant phase equivalent to diapause in insects DIEL fish shrimp siphonophores copepods 104 body length In Pacific more than 43 move 400 m Possibly 25 tons k2 d of migrating biomass with massive consequences for transport of C over world oceans 8 Characteristics of Benthic Boundary Layer BBL Benthic Boundary Layer Benthopelagic Animals Particulate and Dissolved Organic Matter 1 5 of surface production the Low food supply 1 5 of surface primary production reaches reaches BBL BBL Water Epibenthic Megafauna Plankton Sediment Community Sediment Consumer Groups Sediment community bacteria protozoans nematodes polychaetes bivalves crustaceans Epibenthic megafauna holothurians ophiuroids asteroids gastropods sponges Benthopelagic animals fishes squid large crustaceans Plankton bacteria protozoans crustaceans medusae chaetognaths 9 Food Supply to BBL Pelagic sources a Passively sinking particulate organic matter POM including phytodetritus marine snow fecal pellets salp houses and exuvia carcasses b Actively migrating consumer prey plankton nekton c Dissolved organic matter DOM What are the important metabolic demands of a deepsea BBL community Oxygen consumption measured as an estimate of carbon demand in the dominant organisms of each consumer group sediment community epibenthic megafauna plankton and benthopelagic animals oxygen consumption indirect measurement of catabolism which generally accounts for a very significant portion of the food utilized by organisms Measured in situ Santa Catalina Basin first 10 Santa Catalina Basin SCB Metabolic demands of SCB BBL community first whole system study Four consumer groups plankton benthopelagic animals epibenthic megafauna sediment community 11 SCOC in Santa Catalina Basin 25 30 mg C m 2d 1 Epibenthic megafauna Megafauna respirometer on left and picture of SCB bottom with Ophiopthalmus and Scotoplanes on right O normani constitutes 99 of megafaunal abundance and 99 of biomass 12 Ophiophthalmus normani oxygen consumption Plankton bacteria to macroplankton Slurp gun respirometer SGR used to sample mixed macrozooplankton individual megaplankters and platform for syringe samplers for microbial incubations 13 Plankton sampling SGR Transects at discrete depths above bottom Microbial samples at discrete depths Individual Megaplankter collections at discrete depths Mixed macrozooplankton results