Marine Ecology


I. Plankton-   wanders


II. Size  almost all are small


            Table 2.1

            Femtoplankton viruses                                                  0.02-0.2 um

            Picoplankton                bacteria (heterotrophic and photosynthetic)

                                                0.2- 2.0 um

            Nanoplankton               small phytoplankton                              2-20 um

            Microplankton              phytoplankton, zooplankton                  20-200 um

            Mesoplankton              phytoplankton, large zooplankton          0.2-20 mm

            Macroplankton jellyfishes, …                                        2-20 cm

            Megaplankton              jellyfishes, …                                        20-200 cm


            Why are most so small?            Mineral nutrient absorption

                                                            Reduction of sinking rate

                                                            Reduction of predation


III. Phytoplankton

            A. Photosynthesis         6CO2  + 6H2O à C6H12O6      + 6O2


1. Necessary resources carbon dioxide, water, light, chlorophyll, nutrients


                        2. Limitations


                                    a. Light availability

                                                Latitude, season, time of day, suspended matter, ice, clouds


                                                Too little           compensation light intensity


                                                Too much         inhibition


                                    b. Mineral nutrient availability


                                                With depth


                                                With geography


 water depth

 upwelling currents

                                                            terrestrial inputs







                                                Other elements



                                    c. Predation (grazing)


                                    d. Dilution of population


            B. Productivity

                        gC/m2 /unit of time   (usually day or year)


                        cal/m2 /unit of time


                        gross primary productivity – respiration = net primary productivity

                                                                        GPP – R = NPP



                                    1. Oxygen production/ unit of time = NPP


                                                BOD bottle and short incubation

                                                            final oxygen –initial oxygen = NPP


                                                Respiration measured in an opaque bottle

                                                            Initial oxygen – final oxygen = R


                                    2. Carbon 14


                                                add a known amount of radioactive 14C as HCO3


                                                incubate in a BOD bottle for some hours and

then collect particulate matter on a filter


measure radioactivity with a scintillation counter


                                    3. chlorophyll a

                                                a. extract from water sample and measure with a spectrophotometer



                                                b. measure specific wavelength of reflectance from Chl a from a satellite


                                    4. dilution


                        geographic distribution



C. Phytoplankton taxa

1.      cyanophyta  (photosynthetic bacteria)

prokaryotes      very small  picoplankton to microplankton


Prochlorococcus sp.     Picoplankton    perhaps the world’s most numerous organism


                                    Often secrete mucus coating and toxic or distasteful chemical


                                    Therefore, not eaten as readily by zooplankton


                                    Some are nitrogen fixers



2.      diatoms

eukaryotes        small to large  microplankton to mesoplankton


silica shells  (frustules)  fit like lid and bottom of a shoe box


spiny to discourage predation


a few produce toxic chemicals


                                    motile by pseudopodia


                                    buoyancy enhanced by a lipid vacuole


3.      dinoflagellates


eukaryotes        small     nanoplankton to microplankton


some have cellulose case


two flagella for motility


many produce toxic or distasteful chemicals


            red tide, shellfish poisoning, Pfiesteria piscisida


            D. dispersion and dominance

                        Patchy at all scales


                        Blooms common among net phytoplankton


                        More constant populations of picoplankton



                        Dominance of taxa varies with

temperature, salinity, nutrient concentration, season, depth, etc.


            E. abundance of net phytoplankton

                        Low nutrient subtropical gyres (e.g. Sargasso Sea)        1000-10,000 cells/L


                        Inshore coastal (neritic) waters                          100,000 – 900,000 cells /L


                        Estuary                                                             millions of cells/L


                        Gunston Cove                                                              billions of cells/L



IV. Zooplankton

A.     Heterotrophic 

most are herbivorous, some are carnivorous, some are feed on bacteria


B.     Size

Nanoplankton (2 u) to megaplankton (200 cm)


C.     Taxa and abundance



            Flagellates, ciliates, forams, radiolarians, amoebas, etc.

            feed on bacteria and phytoplankton


Copepods        most diverse and most abundant of the net zooplankton

                        Larval stages: nauplius (1-6), copepodites (1-5)


Euphausids       second most abundant


















            salps (thaliaceans), appendicularians (larvaceans)


larvae of benthic invertebrates


larvae of fishes


D.     copepod feeding


E.      microbial loop


F.      vertical migration


G.     zooplankton consumers



larvae and juveniles of most, if not all, species


adults of herrings and anchovies and other, less abundant species


                        benthic suspension feeders


                        sea turtles


                        sea birds (penguins, etc)


                        whales, seals