Zooplankton: who are they? Difflugia Protozoans (protists): Include heterotrophic nanoflagellates (“HNFs”) 1- 20 mm, eat bacteria and smaller HNFs – many prefer hypolimnion Other flagellates, amoeboids (Mastigophora), some of which can migrate vertically (Difflugia) Ciliates: (Paramecium, Stentor, Vorticella) 8-300mm, can be mixotrophic, many are epibionts, or live in sediments Comparatively little known about ecology. One reason is difficulty in studying; note that we hardly got any of these abundant organisms Cyclidium

Rotifers (Phylum Rotifera) Keratella Brachionus Named for the rotating band of hairs called corona 30 mm – 1mm in size, very diverse group Parthenogenic (mostly), with short generation times Only a small portion are planktonic, but those are often quite cosmopolitan and abundant Many are omnivorous, feeding on flagellates, small particles, protozoans Include Keratella, Asplanchna, Filinia, (that we caught) as well as Brachionus, Conochilus

www.spea.indiana.edu Copepods www.stetson.edu/~kwork/images / cyclopoid%20nauplius.jpg Reproduce sexually, with longer generation times (affected also by water temperature) Larger size: 300 – 5mm; likely to be affected by any fish-related size structuring Sexual reproduction, generation times longer (a couple per year) in calanoids Cyclopoid are more predaceous than calanoids, who use currents to collect and select food using modified mouthparts. Calanoids do better than unselective cladocerans at low food quality and quantity (picky) Juveniles of both types are herbivorous, then change in adulthood (in cyclops or large calanoids like Epischura)

Interactions of total zooplankton with chlorophyll: Some trend toward greater abundances of zooplankton where phytoplankton is more abundant

Onondaga, Green, and Oneida Lakes all groups: 1) Greatest abundances in hypolimnion for all (Green monimolimnion not included) 2) Mostly cladocerans in Onondaga and Oneida, more copepods/rotifers in Green Copepods make up more of total in metalimnion (although actually greater numbers in hypolimnion, as we will see) Bar charts Pie charts

Arbutus, Deer, and Wolf Lakes all groups: Greatest abundances in metalimnion (except Deer, where all laters are similar)- However, none of these lakes appear to really be stratified anyway, so differences may be merely chance... 2) Mostly copepods in Arbutus and Deer, more Cladocerans in Wolf 3) Trends for the groups different for each lake... Bar charts Pie charts

Protozoans and rotifers in each lake by layer: Favor either metalimnion or hypolimnion (note Onondaga, which in all cases seems to have increasing numbers with depth)

Break-down of protozoans and rotifers in layers (all lakes averaged): 1) Keratella most abundant 2) Trends hard to determine due to incomplete identification!

Copepods in each lake by layer: 1) Onondaga, Green, and Deer share trend of increase with depth 2) Arbutus and Wolf have greatest in metalimnion 3) Oneida shows reverse trend of 1); greatest in shallow waters

Break-down of copepods in layers (all lakes averaged) 1)Cyclops more abundant in epilimnion, calanoid in metalimnion 2)Hypolimnion unknown due to identification problems...