7 The Water Column Plankton

1. 7The Water ColumnPlankton Notes for Marine Biology: Function, Biodiversity, Ecology by Jeffrey S. Levinton

2. Plankton: Definitions • Plankton: organisms living in the water column, too small to be able to swim counter to typical ocean currents

3. Plankton: Definitions • Phytoplankton • Zooplankton • Mixoplankton (or mixotrophic)

4. Plankton: Definitions • Holoplankton -permanent residents • Meroplankton - temporary residents • Neuston - associated with slick • Pleuston - sticking up above water surface

5. Plankton: Definitions • Size classes

6. Vertical Position of Plankton - Factors • Bulk density - regulated by ionic substitution, gas secretion, and release (cuttlefish, Nautilus) • Swimming behavior • Turbulence stirs plankton through the water column

7. Vertical Position of Plankton - Factors • Size of plankton - smaller plankton, low Reynolds number • Low Re means there is a boundary layer around plankter’s body • Smaller organisms denser than seawater sink with a constant velocity, proportional to organismal volume, although increases of spines etc. can slow sinking

8. Phytoplankton Diatoms • Occur singly or form chains • Size range of nanno to microplankton • Encased in silica shell consisting of two valves • Usually radially symmetrical • Reproduce asexually by binary fission • Also sexual reproduction • Doubling once or twice per day usually

9. (a) Diatoms

10. Thalassiosira Chaetoceros Asterionella japonica

11. Phytoplankton Dinoflagellates • Secrete organic test and have two flagellae • Size range of nanno and microplankton • Asexual and sexual reproduction • Often some life history stages, benthic cysts • Many species are heterotrophic • Often abundant in tropics, mid-latitudes in summer • A few species are the cause of red tides

12. Peridinium (b) Dinoflagellate

13. Phytoplankton Other Groups • Cyanobacteria - abundant, nitrogen fixation • Coccolithophores - unicellular, nannoplankton, spherical, and covered with calcium carbonate plates - coccoliths • Silicoflagellates - unicellular, biflagellate, internal skeleton of silica scales, often in Antarctic, open ocean

14. Cyanobacteria types

15. Bloom of coccolithophores, near Newfoundland Coccolithophore

16. Silicoflagellate

17. Phytoplankton Other Groups • Numerous other groups, including many flagellated types CRUCIAL POINTS ABOUT PHYTOPLANKTON: DIVERSITY IN WATER COLUMN DIFFERENT NUTRIENT NEEDS OF VARIOUS GROUPS (e.g., Fe, Si, Ca, P, N) DIFFERENT PROPERTIES SUCH AS BULK DENSITY, ABILITY TO SWIM

18. Zooplankton Crustacean zooplankton (Arthropods) • External chitin skeleton • Segmentation • Paired jointed appendages (e.g., legs, antennae) • Antennae, mandibles, and maxillae as head appendages • Usually compound eyes • Include copepods, krill, amphipods (crabs, lobsters, sowbugs - not in plankton)

19. Zooplankton Crustaceans - Copepods • Largest group of crustaceans in zooplankton • Range from <1 - a few mm long • Planktonic forms - Calanoida • Long pair of antennae • Swim mainly with aid of 5 pairs of thoracic appendages • Lack compound eyes, medial naupliar eye • Feed on phytoplankton or smaller zooplankton, depending on the species

20. Zooplankton Copepod Feeding Low Reynolds number - viscosity dominates Feeding current (green) generated by thoracic appendages Maxilliped reaches out and grabs particles entrained in current

21. Zooplankton Copepods Females of different species with eggs

22. Zooplankton Crustaceans - Euphausids (Krill) • Shrimplike, up to 5 cm long • Abundant in Antarctic and in upwelling regions • Main food of baleen whales in Antarctic • Feed on phytoplankton and smaller zooplankton • Feeding by means of group of appendages that form a basket - appendages have setae and smaller setules, hairs that capture particles

23. Zooplankton Gelatinous Zooplankton • Jellies include a wide variety of distantly related groups, all have gelatinous material used for support (skeleton)

24. Zooplankton Gelatinous Zooplankton - Cnidaria • Planktonic Cnidaria Scyphozoan jellyfish, Hydrozoan jellyfish (some meroplanktonic jellyfish stages), and siphonophores, specialized colonial and polymorphic cnidarians such as Portuguese man-of-war • mainly carnivores, nematocysts - stinging cells - on tentacles

25. Zooplankton Cnidaria - Scyphozoan jellyfish Note muscular bell and tentacles

26. Zooplankton Gelatinous Zooplankton - Cnidaria Porpita (ca. 10 cm wide) Physophora (50 mm high) By-the-wind-sailor Velella Siphonophores

27. Physalia physalis

28. Zooplankton Gelatinous Zooplankton - Ctenophores • Known as comb jellies • Microcarnivores - feed on smaller zooplankton, planktonic eggs, invertebrate larvae • 8 rows of meridional plates, some have two long tentacles

29. Zooplankton Gelatinous Zooplankton - Ctenophores

30. Zooplankton Gelatinous Zooplankton - Salps • Related to benthic sea squirts, but have incurrent and exit siphons on opposite ends of body • Solitary or colonial (up to 2 m in length) • Have a tail, typical of tunicate swimming larvae • Small, only a few mm long • Tail generates current through house, current is strained by fine fibers that trap food Gelatinous Zooplankton - Larvacea

31. Salps Instructor: recommend use of http://www.whoi.edu/cms/images/oceanus/salp_550_59911.jpg

32. Zooplankton Arrow worms • Torpedo shaped, a few cm in length • Rapid swimmers, carnivorous

33. Zooplankton Pteropods • Holoplanktonic snails • Swim by means of lateral projections from foot • Suspension feed or are carnivorous, depending upon species

34. Zooplankton Planktonic polychaetes • Have very well developed parapodia Instructor: Use, for example http://www.tmbl.gu.se/staff/FredrikPleijel/03Tomopteris_helgolandica.jpg

35. Zooplankton Protistan zooplankton - Foraminifera • Secrete skeleton of calcium carbonate, sometimes with great ornamentation • Common in plankton • Size ~ 1 mm to a few mm • Contractile pseudopodia trap food particles • Foram ooze - deep-sea sediment

36. Zooplankton Protistan zooplankton - Radiolaria • Skeleton of silica, sometimes with great ornamentation, occurs singly and as colonies, depending on species • Common in plankton • Size ~ 50 m to a few mm • A membrane separates interior cell from exterior cytoplasm, which streams out something like foraminifera • Radiolarian ooze - deeper than foram ooze

37. Protistan zooplankton - Ciliates Zooplankton • Common in plankton, feed on bacteria, smaller phytoplankton, some mixotrophic • Elongate, ranging from size from about 50 m to over 1 mm in length, covered with rows of cilia Strombidium, 80m long Strombidium sp. Under UV light, ingested chloroplasts in red Photos by Diane Stoecker

38. Phytoplankton and Microbial Diversity - Molecular Techniques • Problem of high diversity, enumeration in samples • Important issue is function of cells; e.g., photosynthesis, nitrogen transformation • Many plankton photosynthesizers and bacteria are morphologically difficult to identify • Need other techniques to use probes to count different cell types

39. Phytoplankton and Microbial Diversity - Molecular Techniques • First need to collect sample and sort by cell size

40. Phytoplankton and Microbial Diversity - Molecular Techniques • Immunofluorescence: develop antibodies to specific species, produce antibodies, tag antibodies with fluorescent dye, enumerate dyed cells by fluorescent reaction to uv light source • Monoclonal antibodies: allows more specific antigen-antibody reaction to specific proteins in cell

41. Phytoplankton and Microbial Diversity - Molecular Techniques Example: immunofluorescence staining targetted at cell surface proteins of red tide dinoflagellate Alexandrium tamarense (yellow)

42. Phytoplankton and Microbial Diversity - Molecular Techniques • DNA analysis using Polymerase Chain Reaction (PCR): • Primers (short chain nucleotides) from known DNA of a species can be used to bind to DNA of a cell and then can be amplified and identified, even quantified relative to other sequences (quantitative version of PCR)

43. Phytoplankton and Microbial Diversity - Molecular Techniques PCR involves steps of breaking up DNA into chains (denaturation), adding primers (annealing) and nucleotides, and new DNA sequence is synthesized (extension) through steps of heating and cooling

44. Phytoplankton and Microbial Diversity - Molecular Techniques • High Throughput Sequencing - It is possible now to sequence entire genomes; extreme example is shotgun sequencing, involving complete sequencing of an entire water sample of cells (See Hot Topics 7.1)

45. Phytoplankton and Microbial Diversity - Molecular Techniques • Microarrays: DNA sequences are extracted from an organism, and a library of sequences is recorded; sequences are synthesized and put on a chip; sample is added to chip and complementary sequences in sample binds to appropriate spots on chip. • Allows for enumeration of known sequences in a water sample

46. Phytoplankton and Microbial Diversity - Molecular Techniques • PCR study of nitrogen-transforming microbes. Allows relative abundance of different types (e.g., nitrogen-fixers; denitrifiers) - see Ward, B. and O’Mullan 2002, references in text) • PCR study of microbes as function of depth; allows complete survey of known microbes in plankton as function of depth. Allows us to see when photosynthesizers stop with a given depth (e.g. survey of Pacific microbes with depth - see DeLong et al. 2006, references in text)

47. The End