1. Zooplankton processes Puget Sound Oceanography Jan. 28, 2011

2. Plankton – “that which is made to wander or drift” organisms that float or weakly swim through water Phytoplankton – organisms that use sunlight to fix carbon Zooplankton – the animal portion of the plankton; herbivorous, carnivorous, or mixed Autotrophs – fix their own energy from inorganic substances (producers). Heterotrophs – depend on energy fixed by others (consumers) Mixotrophs – do both Holoplankton – are planktonic through their whole life cycle Meroplankton – are planktonic only during part (usually larval) stage of their lives Herbivores Carnivores Omnivores

3. Characteristics of estuaries: Highly advective Strong gradients Fronts / mixing Very productive Benthic / pelagic coupling High abundances of organisms Terrestrial influences Human influences

4. Special challenges for estuarine species: tolerating / responding to strong gradients overcoming advection predator density contaminants / pollution altered food webs Zooplankton need: food to avoid predators find good growth habitat find mates ‘life cycle closure’

5. Species are zonated along gradients of salinity: Species composition (meso-zooplankton): Freshwater Moderate diversity: Cladocerans (e.g., Daphnia) Freshwater molluscs Typically 5-7 species of copepods Freshwater jellyfish (rare) Truly estuarine a few species of calanoid copepods, usually 1-2 dominant Meroplankton (bivalves, barnacles, crabs) jellyfish Oceanic high diversity of copepods (>30 spp) amphipods euphausiids jellyfish meroplankton (echinoderms, bivalves, barnacles, crabs)

6. Zonation of species distributions along salinity gradients: Cumulative salinity distribution of common zooplankton in San Francisco Bay Kimmerer (2004) E. affinis = Eurytemora (a copepod)

7. Species richness in estuaries follows a long established pattern along the salinity gradient described by Remane (1934) Salinity gradients (species patterns set by tolerance) - diversity lowest in brackish water (5-10‰) Why??

8. Species gradients also set by behavior: Acartia tonsa is only found in estuaries and nearshore environments. H0: they cannot feed effectively on very low phytoplankton concentrations. Paffenhoffer et al, 1988 (Food) (Feeding)

9. Egg Nauplius (6 stages) Copepodites (5 stages) Adult Crustaceans Copepods ~ 1 month to complete Microzooplankton: rapid reproduction and growth. Highly dependent on food and temperature. At maximum, doubling rates in hours! Jellyfish: annual life cycle, growth to 0.7 d -1

10. Generalized seasonal cycles of phytoplankton and zooplankton biomass: Zooplankton Phytoplankton J F M A M J J A S O N D Late, single bloom Early, bi-modal bloom

11. Difference of ~1 month between Main Basin and Dabob Bay phytoplankton blooms and copepod reproduction 1 st appearance of young life stages (purple) Calanus marshallae Calanus pacificus Percent composition Dabob vs. Main Basin Phytoplankton productivity Dabob vs. Main Basin Zooplankton

12. Zooplankton diel vertical migration (DVM): Who migrates? Crab larvae Shrimp Large copepods Euphausiids Some Jellyfish Some Amphipods Chaetognaths Pteropods

13. Magnitude of Diel Vertical Migration by Life Stage 0 25 50 75 100 125 150 175 200 Egg Calyptopis F1F2F3F4 F5/6 F7 Juvenile Adult Life History Stage Depth (m) Average daytime depth Average nighttime depth Range of migration

14. River end Ocean end Vertical migration in 2-layer circulation

15. Some may migrate on tidal cycle for transport: Fernandes et al. 2002

16. http://northweb.hpl.umces.edu/videos_animations/Oyster_Larvae_Animations.htm North et al, MEPS 2008

17. Copepod abundance #/m 3 Ctenophore abundance #/m 3 Gelatinous predator predation on zooplankton in Chesapeake Bay Inverse relationship between calanoid copepod and Mnemiopsis leidyi densities at two stations in Chesapeake Bay.

18. Optical Plankton Counter (OPC) OPC mounted on a ScanFish