Life in the Pelagic: An introduction to the Plankton Size classifications and terminology • Classification of planktonic organisms is generally based upon size – rather than function (most methods involve filtration which distinguishes organisms based upon size rather than species). • This can be problematic because in the plankton, trophic position is not always determined by size (size ratios between predator and prey are not constant). Abundance of living organisms Organism and size Typical abundance Bacterioplankton (~1um) 105 to 107 per ml Nanoflagellates (1-10um) 102 to 104 per ml Protizoan plankton (20-50um) 10 to 102 per ml Phytoplankton (20-200um) 10 to 104 per ml Humans (2m) 6x106 in Washington State Bacterioplankton in Aquatic Systems • Found in all natural waters • Non-pathogenic! • Small (≤1µm) yet abundant (>106 cells ml-1) • Comparable in biomass to phytoplankton • Fundamental in nutrient & carbon cycling • Drive water quality parameters (i.e. anoxia, nutrient availability) • Extremely diverse 10 µm (DAPI stained slide of bacterioplankton from Chesapeake Bay) Femtoplankton (0.02 – 0.2 µm) Bacteriophage •Diverse and ubiquitous viral community in the marine environment •Significant role suspected (certainly impact bacteria and may also impact primary production and higher trophic levels, viruses suspected in some marine mammal beachings). •Viruses may be important agents in demise of some phytoplankton blooms (e.g., Trichodesmium) •Viruses are important agents for DOM release and nutrient cycling 0.1um Picoplankton (0.2 – 2 µm) Bacteria Archaea •Very important role in marine food webs, •Distinct RNA especially degradation and recycling •Early evolutionary separation •Ubiquitous in ocean (~106 / ml) •Favoring extreme environments •Various forms (motile, rods, spiral, coccoid) •Recently discovered in ocean Picoplankton (0.2 – 2 µm) Vertical distribution of Bacteria and Archaea cell abundance at HOTS (Karner et al 2001). • Opposite patterns of distribution • Archaea are ubiquitous, but biogeochemical significance is poorly understood More on Picoplankton (0.2 – 2 µm) Cyanobacteria – “blue-green algae” Photosynthetic bacteria e.g. Synechococcus spp. • Up to 106/ml in euphotic zone • In both coastal and oceanic waters • In temperate and tropical oceans • Can play major role in primary production, especially open ocean Prochlorophytes •Prochlorococcus marinus •Abundant at base of the euphotic zone in open ocean (106 / ml) •Ubiquitous distribution •Can play a major role in primary production, especially in the open ocean •Different strains have been identified that live in different depths in the water column and have different metabolic capabilities particularly with respect to what forms of nutrients they can use, i.e., NH4 vs. NO3. Note: Prochlorococcus is currently believed to be the most abundant form of plant life on earth. 2µm Nanoplankton (2 – 20 µm) Mostly small eukaryotic phytoplankton Dominate more oligotrophic open ocean environments dinoflagellates small centric diatom small pennate diatom coccolithophorid Microphytoplankton (20 – 200 µm) Large eukaryotic phytoplankton Prominent in productive coastal / upwelling zones Heterosigma large dinoflagellates chain-forming diatoms centric diatom Microzooplankton (2 – 200 µm) These are heterotrophic and mixotrophic protozoans •Large group and taxonomically diverse • ciliates • dinoflagellates • heterotrophic nanoflagellates (HNFs) • radiolarians (silica) and foraminifera (calcite) •Same size as the microphytoplankton (2 – 200 µm) Oxyrrhis marina •Heterotrophic and mixotrophic forms •Very important consumers in marine environments!!! Tintinnid ciliate Heterotrophic nanoflagellates bodonids choanoflagellates Dinoflagellates Protoperidinium Noctiluca scintillans Gyrodinium spirale Favella-like tintinnid Ciliates Eutintinnis Laboea strobila Favella-like tintinnid http://www.aslo.org/photopost Leegaardiella sp. Let’s talk about grazing… Sarcodines: foraminifera Sarcodines heliozoa radiolaria amoebae Mesozooplankton (200 um – 2 mm) • Relatively large, planktonic heterotrophs (200 µm – 2 mm) • Huge, diverse group… • Larger protozoans • Coelenterates • Cheatognaths • Annelids •Molluscs • Arthropods • Copepods • Amphipods • Euphausiids • Small larvaceans and salps • Pteropods and heteropods Meroplankton •As opposed to holoplankton or true plankton •Eggs, larvae and juvenile stages of benthic invertebrates and fish •Time spent in the plankton may be minutes to months •Especially important in coastal and estuarine waters as you will see on the zooplankton lab Polycheate larvae Snail veliger Starfish larvae Sea urchin larvae Barnacle nauplius Crab zoea Barnacle cypris Crab megalopa Macroplankton (2-20 cm) and Megaplankton (20-200 cm) Scyphozoan medusa (Chrysaora) Ctenophores like Mnemiopsis and Beroe (megaplankton) (macroplankton) • “Jellyfish” are prominent examples • Most are classified as plankton • Hydrozoan, Scyphozoan and Cubozoan medusae • Ctenophores •Salps • Larvaceans • Pteropods and Heteropods Major Phytoplankton Groups Major Phytoplankton Groups 1) Diatoms (20um to 2mm) • Most abundant, rapidly dividing organisms, bloomers • Silicate frustrule (shell) – pennates (motile) and centrics • Solitary and chain forming 2) Dinoflagellates (20 – 40um) • Motile with flagella • Auto, mixo, hetero-trophic • HABs (paralytic shellfish poisoning, Gymnodinium, red tides (Prorocentrum), Pfiesteria piscicida, zooxanthellae • Noctiluca sp. (bioluminescence) 3) Microflagellates (2-30um) • Coccolithophores, primnesiophytes, cryptophytes 4) Picophytoplankton (<2um) • Prochlorococcus and Synechococcus Diatoms Thalassiosira anguste Chaetoceros convolutus Pseudo-nitszchia multiseries Chaetoceros debilis Cylindrotheca sp. Dinoflagellates Ceratium tripos Dinophysis Gymnodinium spp. Protoperidinium Other phytoflagellates cryptomonads Chrysochromulina Emiliania huxleyi bergeri Phaeocystis globosa Pyramimonas Chlorella Dunaliella Chlorophytes and other coastal taxa Heterosigma akashiwo Euglena Picophytoplankton Mixed assemblage under epifluorescence Synechococcus Prochlorococcus N2-fixing cyanobacteria as endosymbionts in the diatom Rhizosolenia Trichodesmium spp. .