The Oceanic Carbon Cycle: Biological Pump Primary producers: who are they? How does the pump work: transport to the bottom Open ocean ecosystems

high diversity: DEEP SEA

Deep-Sea : diverse life forms Deep-sea thought to be without life (‘azoic’) until 19 th century deep-sea exploration expeditions ‘Erebus’ and ‘Terror’, , James Ross Clark ‘Lightning’ and ‘Porcupine’, , Wyville Thompson ‘Challenger’, , Wyville Thompson, J. W. Murray (Foraminifera:H.B. Brady, 1884)

Satellite data (CZCS, SeaWIFS) SURFACE OCEAN PRIMARY PRODUCTIVITY High productivity: input of nutrients (N, P) from land Seasonality

Oceanic spring bloom (high-mid latitudes) Winter: light limitation (insolation, storms mix phytoplankton below photic zone) Nutrients not (fully) used; accumulate Spring: more light, warming causes stratification, keeps plankton within photic zone Bloom (until nutrients used up, zooplankton eats phytoplankton)

EUKARYOTES (multicellular): Fungi Animalia Plantae Molecular phylogenies: Protein sequences Small subunit RNA ‘PROTISTS’: EUKARYOTES (unicellular) PROKARYOTES

Oceanic primary producers: Prokaryotes (unicellular, ‘simple’ cell, asexual reproduction; 0.6  m) - cyanobacteria Prochlorococcus, Synechococcus): up to ~2/3 of primary productivity in the oceans Eukaryotes (complex cell - nucleus - sexual and asexual reproduction; tens of  m) –Bacillariophyceae - Opaline Silica skeleton: Diatoms –Haptophyceaea Calcium-carbonate skeleton: Calcareous Nannoplankton No skeleton: Phaeocystis –Dinophyceae - organic -walled cysts: Dinoflagellates

(Haptophyte Algae) Diameter ~20-30  m CALCAREOUS NANNOPLANKTON COCCOLITHOPHORES Polysaccharide gels (transparent exopolymer particles)

Planktonic foraminifer

Prymnesiophytes (Haptophytes) - Phaeocystis Polysaccharide gels (transparent exopolymer particles)

Transparent Exopolymer Particles Phaeocystis blooms at high latitudes (survive in sea ice) ~10% of annual global marine primary productivity Much of this in form of gels - major part of dissolved organic carbon in oceans Secrete dimethylsulfide - add sulfur to atmosphere

Diatoms Today up to 20-40% net primary production, ~ 50% organic carbon exported

Diatoms Rapid delivery of diatoms to sea floor in frontal zones (Kemp et al., 2006) ‘giant diatoms’ in mats e.g., Fragilariopsis, Thalassiothrix, Rhizosolenia

Dinoflagellates Dinophyceae

Dinoflagellates: harmful algal blooms (HABs)

Type of primary producers/productivity of oceans: Open ocean, low productivity (central gyres): prokaryotes, some dinoflagellates Open ocean, higher productivity: calcareous nannoplankton Open ocean, highest productivity: diatoms, Phaeocystis Coastal ocean, high productivity: dinoflagellates, Phaeocystis

Oceanic primary productivity: different dominant producers - ‘fertility’ ANNUAL

Deep-sea environment: cold, dark, high pressure, very little food. Food supplied by surface productivity, miles up: biological pump

How much food reaches the bottom? Not very much (<1 to few % of PP) e.g., Martin et al., 1987; north-east Pacific stations F=1.53(z/100) z=depth

Oceanic food chain

Food from surface to bottom: biological pump how does it work? Marine snow (~4 mm particle, dead and dying phytoplankton, zooplankton exoskeletons, fecal matter) m/day

Organic matter from surface to bottom:biological pump Ballasted by –silica (diatoms) –carbonate (foraminifera, nannoplankton) –terrigenous dust In fecal pellets Stuck together by polysaccharides (Phaeocystis, diatoms, cyanobacteria, calcareous nannoplankton) In ‘giant balls of mucus’ - larvacean houses Carrion falls (‘dead whales’) Lateral transport (refractory organic matter) Discrepancy between food requirements of faunas and supply in sediment traps: faunas need more than what is delivered

Larvacean ‘houses’ (tunicates) 2-3 feet diameter Tunicates are Chordates (related to us vertebrates - lancelet fish)

We do not understand transport of organic matter to the sea floor in the present ocean, nor importance of prokaryotic productivity We can not predict the effects of global warming and increased nutrients on carbon cycle in the oceans

Oceanic primary productivity - how limited? Transport to sea floor - how limited? Can we manipulate (carbon sequestration)?

In some regions N and P are NOT limiting "high-nutrient, low- chlorophyll” (HNLC) regions, e.g. equatorial Pacific Not enough iron (Fe)