1. Holoplankton – spend entire life in plankton (e.g. copepods, chaetognaths, Daphnia, etc)
2. Meroplankton – spend part of life in plankton (larvae of fishes, invertebrates)

1. Acartia tonsa, A. clausi abundant and widespread species in estuaries 2,933/m² in Florida estuary
1. Can comprise 80 –90 % of numbers in plankton
2. 0 – 70 ppt broad salinity tolerance (euryhaline)
3. 0 – 40 ° C broad temperature tolerance (eurythermal)
2. Other genera: Temora, Eurytemora, Paracalanus, Oithona, Labidocera, Centropages, Undinula
3. Some special terms for life stages of copepods:
1. nauplii – small just hatched larval stage (< 250 m m)
2. copepodites – looks like small adult, but non-reproductive intermediate stage (250-850 m m)
3. adults – large stage, reproductive (850-1000 m m)

1. Mysids (Mysidacea) – small crustaceans
2. Daphnia (water fleas) – in freshwater parts of estuary

1. Sagitta – found worldwide, abundant, in its own phylum, larval fish predator of great importance

1. Mnemiopsis – Ctenophore that is a predator on larval fishes

1. Polychaete larvae – trochophore (Nereis, Notomastus)
2. Crustacean larvae – nauplius, cyprid (barnacles Balanus), zoea, megalops (crabs Callinectes)
3. Mollusc larvae – velliger (gastropods Littorina, oysters Crassostrea, mussels, Mytilis)
4. Cnidarian larvae – planula, medusa (Aurelia)
5. Echinoderm larvae – pleuteus larvae (Asterias)

1. Tunicate larvae (tadpole larvae) – Ectinocidia
2. Fish larvae and eggs – Pinfish Lagodon rhomboides, Spot Leiostomus xanthurus, weakfish Cynoscion regalis , to name but a few

1. Many are too small for plankton nets (which are as small as 80 m m)
2. May be underestimated in zooplankton surveys (twice as abundant as the net zooplankton)
3. Taxa in the microzooplankton
1. Tintinids (ciliates)
2. Flagellates (protozoans)
3. Rotifers (metazoans)

1. Zooplankton are herbivores on phytoplankton - highest peaks in Spring and Summer for zooplankton
2. Rapid changes in abundance are possible - "blooms" - in response to phytoplankton growth spurts
3. During spawning periods of fishes and invertebrates, meroplankton can dominate plankton numerically

1. Canadian arctic, Eskimo Lakes/Liverpool Bay (Fig. 8.4) - peak in summer (June & July); copepods, polychaetes and barnacles
2. Raritan Bay, NJ (Fig. 8.2) - Acartia tonsa peaks in June & July, present April through February, lowest in Winter Spring; absence of all stages in March.
3. Card Sound, FL (Fig. 8.3) - Peak macrozooplankton in Jan ---> May, Sep --> Dec. Low abundance in summer. Microzooplankton remain high in summer

Geographic Area	Total macro-zooplankton (no./m3)	Acartia adults	Acartia im-mature forms	Other copepods	Mero-plankton
Florida	3,765	75 %	16 %		8 %
South Carolina	9,258	20 %	18 %	30 %	24 %
Virginia	20,191	13 %	67 %	7 %	11 %
Maryland	1,425	61 %		36 %	1 %
New Jersey	8,052	32 %	29 %	17 %	9 %
Canada	121,000	4 %	41 %	12 %	3 %

1. Card Sound, FL : 50,000 --> 200,000 microzooplankters/m³ (Reeve and Cosper 1973)
2. Long Island Sound: 1000 --> 10,500 microzooplankters/L (or 1,000,000 ---> 10,500,000 microzooplankters/m³ ) (Capriulo & Carpenter 1980)
3. Terrebonne Bay, LA: (Gifford & Dagg, 1988):

Microzooplankton taxa	Number of cells/L	Number of cells/m3
Tintinids	540-->1400	540,000 -->1,400,000
nonloricate ciliates	3160-->20360	3,160,000-->20,360,000
other ciliates	420-->3500	420,000-->3,500,000
zooflagellates	18,000	18,000,000
Totals	22,120-->43,260	22,120,000-->43,260,000

1. Compare these estimates with the abundances of the macrozooplankton above. Notice that the microzooplankton are numerically dominant.

1. Copepods are important as larval fish food
2. Copepods are larval fish predators
3. Food chain: phytoplankton --> copepods ---> larval fish
4. Also: phytoplankton --> microzooplankton (rotifers) --> larval fishes---> macrozooplankton (ctenophores/chaetognaths/copepods)

1. Temperature
1. In arctic: 1-2 generations/year for Acartia clausi
2. In Massachusetts: 1-2 generations/year for Acartia clausi
3. In Florida: 11 generations/year for Acartia tonsa
4. Time to reach maturity varies with temperature for Arcartia tonsa in Pautuxtent River, MD (Heinle 1966):

Temperature ° C	Days (egg to egg)
15.5	13
22.4	9
29.5	7

 

2. Food (phytoplankton) is limiting at times
1. Copepods graze 2 - 50 % of the phytoplankton production
2. Phytoplankton production does not always provide sufficient energy for the copepod populations; detritus often makes up the difference (Heinle & Flemer 1975)

1. Feeding is on nanophytoplankton; heterotrophic bacteria; detritus;
2. Microzoplankters can consume 40-45 % of bacterioplankton (Sherr et al. 1986) or up to 88 % of the nanophytoplankton production (Paranjape 1987)
3. Tintinids are eaten by Acartia, Uca (fiddler crab larvae)
4. Population doubling times: 10 - 20 hours possible