Bay of Quinte Remedial Action Plan Assessment of the State of Impairment of Beneficial Uses: II. Zooplankton.

Summary from Original Document

Prepared for Fisheries and Oceans Canada and Environment Canada

by

Ora E. Iohannsson' and Ken H. Nicholls'

'Great Lakes Laboratory for Fisheries and Aquatic Sciences Department of Fisheries and Oceans 867 Lakeshore Rd. Burlington, ON L7R4A6

'S-15 Concession I, RR # 1, Sunderland, Ontario LOC IRO Lake Ontario's Bay of Quinte has been identified a.s one of 42 Areas ofConcem in American and Canadian waters of the Great Lakes for which a Remedial Action Plan (RAP) is required as directed under the bi-national GreatLakes Water Quality Agreement. Most aquatic ecosystem problems in the Bay of Quinte are related to eutrophication caused by excessive nutrient loading and to degradation ofthe fish community through elimination/depression oftop predatory species and invasion of exotic species. These bottom-up and top-down forces have resulted in altered biological communities. Eutrophication impacts zooplankton communities in several ways: it can alter habitat conditions, food quality and feeding, and predation patterns of other interacting biotic components ofthe aquatic system. Zooplankton community structure is often altered as a result. Similarly, altered fish communities, especially those where planktivorous fish become dominant, reduce individual mean size and grazing capability of the zooplankton community as well as change community structure. Much progress has been made in the last 25 years in reducing point-source loading of phosphorus in order to rehabilitate the Bay of Quinte. Fish communities resurged with the development of the walleye and lake whitefish populations, and the decline of white perch in the 1980s. Further changes have occurred in the late 1990s with the decline in lake whitefish, redistribution of walleye and resurgence of yellow perch, all associated with the colonization of Lake Ontario and the Bay of Quinte by dreissenid mussels. The major purpose of this report is to assess the Beneficial Use Status of the zooplankton in the Bay of Quinte by examining long-term trends in the crustacean zooplankton community with emphasis on those changes that may be related to rehabilitation of the Bay of Quinte ecosystem and to the recent (1995) establishment of zebra mussels in the bay. A variety of data analysis approaches utilizing both univariate and multivariate methods have been applied to the problem. An integral part of this assessment was the inclusion of zooplankton data from three other reference locations that may serve as analogues for a less perturbed upper Bay of Quinte. It is suggested that the reference location zooplankton communities can thus serve as restoration targets for the upper bay. Comparisons of community structure have been supplemented with comparisons of zooplankton biomass, mean size and ratios of predatorlherbivore biomass

2 which reflect patterns of energy flow through the system. This assessment uses a 24-year data series collected under Project Quinte, a multi-agency collaborative study of long­ term change in the Bay of Quinte. Sixty species of crustacean zooplankton have been identified in the Bay of Quinte samples, including 41 cladoceran species, 10 cyclopoid

.~ copepod species and 9 calanoid species. Most common were Bosmina longirostris, Ceriodaphnia lacustris, Chydorus sphaericus, Daphnia galeata mendotae, D. retrocurva, Diaphanosoma birgei, Cyclops vernalis, Diacyclops thomasii, Mesocyclops edax and , Tropocyclops extensus. The distribution of zooplankton species in the Bay of Quinte reflects a spatial gradient in eutrophy and habitat structure (water depth, temparature and thermal structure of the water column) from the shallow, warm, eutropic, upper bay to the deep (32 m), thermally-stratified, mesotrophic lower bay. A significant change in species richness over time was observed only at station (HE) in the middle of theBay of Quinte. Here, reductions in species richness averaged 0.23 species/year, with a total reduction in species number of21 % between 1982 and 2000. Very low species numbers (11 and 13) were recorded during 1992 at Stations Band HB, respectively, which likely was related to record low water temperature during that year (although the mechanism is unclear). The zooplankton community structure showed considerable spatial dissimilarity as well as temporal change. Multivariate analyses of species composition illustrated how zooplankton community composition shifted firstly with the decline in phosphorus loading and concentrations (1979-1981/2), secondly with the change in the fish community (1982/3-1991), thirdly with the climatic event (cold spring in 1992) caused by the eruption of Mount Pinatubo in 1991 (effects observed only in 1992 (Station C) or later, 1994 (Station B», and fourthly with the invasion of dreisenids (1995-2000). At each of these junctures, the zooplankton community composition changed position in "community" space. At these same junctures changes in community function were also observed. It should be noted that 2000 was also an unusual year and the reasons for these differences are not currently understood. The response ofthe zooplankton community to decreases in P loading are difficult to distinguish due to changes in the fish community in the 1980s. Changes consistent with decreases in P were declines in the densities of Chydorus sphaericus, Eubosmina coregoni and Cyclopos vernalis. Cluster analysis also indicated that the zooplankton'

3 community in later years at Station B was similar to that at Station HB in the early years. of the study: HB always had lower total phosphorus levels than Station B. Declines in P­ loading appeared to· have relatively more impact at Station C than the other sites. Comparisons of zooplankton community structure between the pre-phosphorus control

.~ years of 1975-76 and the more recent pre- and post Dreissena years revealed that the differences were most significant at Station C and least significant at Station B. Increases in the biomass of piscivores (walleye, large white perch) in the bay in the early 1980s were associated with dramatic changes in the zooplankton community. Total zooplankton biomass, Daphnia biomass, and mean individual length increased with the increase in piscivore biomass. Some zooplankton species increased while others decreased. In total, 33 taxa significantly increased over the 1975-1994 time period, while 18 taxa decreased. Significant increases were found for Daphnia galeata mendotae, and decreases for Leptodora kindtii at all three sampling stations. Other trends included increased densities of benthic cladocera, Bosmina longirostris, total Daphnia sp. and Holopedium gibberum in the middle and lower bay, but not in the upper bay. Daphnia pulicaria, Skistodiaptomus oregonensis, benthic copepods, total adult calanoids and Mesocyclops edax all increased in the upper and middle bay, but not in the lower bay. Chydorus sphaericus, and total calanoid copepodids declined in the middle and lower bay, but not the upper bay, and Diaphanosoma birgei decreased in the upper and middle bay over the 1975-1994 period. Zebra mussels (Dreissena) invaded the Bay of Quinte in the mid-1990's; 1995 is considered to be the earliest year of a significant Dreissena population in the bay. With the arrival of dreissenids, zooplankton total biomass decreased at all three sites even though zooplankton mean length did not change. This indicates that the decline in biomass was not related to changes in the level of predation on zooplankton by fish. The declines are most likely related to effects of dreissenids on food resources. The ratio of predatory to total zooplankton biomass also decreased at all sites with a decrease in the percentage of cyclopoids in the communities. Thus the relative importance of the "grazer pathway" in the pelagic foodweb increased and the relative importance of the microbial loop, which is dependent on predation by zooplankton to transfer energy up the foodweb to fish from ciliates and rotifers, decreased.

4 In tenns of specific species effects - only two crustacean zooplankton species or taxon groups at Station B, three at Station HB and four at Station C showed significant differences between pre- and post Dreissena 6-year time periods (1989-1994 vs 1995- 2000); however it has not been possible to detennine conclusively that the observed

.~ changes in any of these taxa were caused by the establishment of Dreissena. The best case for a Dreissena effect might perhaps be made for those zooplankton taxa that showed a significant change in the 6-year pre- and post Dreissena comparisons, following the absence of a significant longer tenn trend in the 1975-1994 data series .. Taxa fitting this condition include declines in Chydorus sphaericus at Station B (-67 %), Daphnia pulicaria at Station C (-94 %), total cyclopoid copepodids at Stations B (-67 %) and C (-57 %), and increases of317 and 186 %, respectively, at Stations HB and C, in total calanoid nauplii. The multivariate data analysis revealed an altered and less stable community structure after dreisenids invaded; also, different species were involved in these changes than those observed with decreases in P-Ioading. Comparisons of community structure between the reference lakes and the upper bay after dreissenid arrived (1995-2000), indicated that a trend towards a less perturbed state in the upper bay, would have to include reductions in the densities of Eubosmina coregoni, Daphnia retrocurva, Chydorus sphaericus and Daphnia galeata mendotae and increases in Bosmina longirostris, Daphnia pulicaria, total calanoid copepodids, littoral cladocerans, Leptodiaptomus minutus and Diacyclops thomasi. These 10 species/taxon groups accounted for more than 50 % of the dissimilarity between the upper Bay of Quinte (1995-2000) and reference lake zooplankton corinnunities. Potential barriers to the re-establishment of zooplankton communities typifying a less eutrophic Bay of Quinte might include: 1) an imbalanced fish community consisting of excessive biomass of zooplanktivores relative to piscivores, , 2) an imbalance in, and/or a depletion of food resources (small-celled phytoplankton species) resulting from the establishment of Dreissena, and 3) establishment of other exotic, invading species (e.g. Bythotrephes, Cercopagis, Neogobius) with potential to impact directly (by predation) on important zooplankton species. While the reference lake approach used here seems to have been appropriate for evaluation of upper Bay of Quinte zooplankton community rehabilitation, the lakes used

5 in this exercise are not suitable for a similar assessment of the lower bay. Future work on this subject should endeavor to obtain zooplankton data from some other deep-water embayments of the Great Lakes (e.g. Twelve-Mile Bay o{Georgian Bay and South Bay on Manitoulin Island) that could serve as analogues for a les~ stressed lower Bay of Quinte and thus as restoration targets for lower bay zooplankton community structure in . the same way that the upstream Trent-Severn Waterway locations have served for the upper bay. In conclusion, eutrophication, high levels of planktivory and possibly other related stresses apparently contributed to a perturbed crustacean zooplankton structure in the Bay of Quinte. Prior to major reductions in point-source phosphorus loading in 1977 when the fish community was still dominated by planktivores, zooplankton community structure in the upper bay was most unlike those of reference (target) lakes. Since then, however, there have been changes that may indicate some recovery; these were manifested at the whole-community level by increases in total biomass, mean individual size, ratio of large/small Daphnia biomass, decreases in predatory ratio, and changes in community composition to a structure more similar to that represented in the reference lakes. Increased inter-armual variability in zooplankton community structure in the upper and lower bay was associated with the establishment of zebra mussels in the bay in 1995. Decreases in the relative abundance of cyclopoids with the arrival of dreissenids, the marked decrease in zooplankton biomass and mean size in 2000 and the potential impacts of Cercopagis pengoi and Neogobius melanostoma are cause for concern with regards to the 'integrity' of the zooplantkon community. They will need to be evaluated with respect to a final expected 'normal' zooplankton community.

6 • •

Bay of Quinte Remedial Action Plan Assessment of the State of Impairment of Beneficial Uses: II. Zooplankton.

Summary

Prepared for Fisheries and Oceans Canada and Environment Canada

by

Ora E. Johannsson 1 and Ken R. Nicholls'

LGreat Lakes Laboratory for Fisheries and Aquatic Sciences Department of Fisheries and Oceans 867 Lakeshore Rd. Burlington, ON L7R 4A6

'S-15 Concession I, RR # I, Sunderland, Ontario LOC IRO The major purpose of this report is to assess the Beneficial Use Status of the zooplankton in the Bay of Quinte. Long-term trends in the zooplankton community were examined with emphasis on those changes that may be related to rehabilitation of the Bay of Quinte ecosystem and to the recent (1995) establishment of zebra mussels in the bay. This assessment uses a 24-year data series collected under Project Quinte, a multi­ agency, collaborative study of the Bay of Quinte, and a 2-year data series from a set of reference lakes which should be comparable to the upper bay. Comparisons ofthe seasonal mean zooplankton biomass, mean body length and ratio of predatory/herbivore biomass provided additional information on changes in energy flow through the food web associated with changes in the zooplankton community. Lake Ontario's Bay of Quinte has been identified as one of 42 Areas of Concern in the Great Lakes for which a Remedial Action Plan (RAP) is required as directed under the bi-national Great Lakes Water Quality Agreement. Most problems in the Bay of Quinte are related to eutrophication caused by excessive phosphorus loading to the bay and to degradation of the fIsh community through elimination/depression of top predatory species and invasion of exotic species. These forces have resulted in altered biological communities. Eutrophication impacts zooplankton communities in several ways: it can alter habitat conditions (e.g. oxygen levels) and predation by fish and invertebrates. Fish communities dominated by plankton-eating fish (planktivores) reduce zooplankton mean size. Smaller zooplankton have a lower capacity for grazing down the phytoplankton than larger herbivorous zooplankton. Both eutrophication and predation can change zooplankton community structure. Much progress has been made in the last 25 years in reducing point-source loading of phosphorus in order to rehabilitate the Bay of Quinte. A more balanced fish community of piscivorous and planktivorous fish resurged with the development ofthe walleye and lake whitefish populations, and the decline of white perch in the 1980s. Further changes have occurred in the late I 990s with the decline in lake whitefish, redistribution of walleye and resurgence of yellow perch, all associated with the colonization of Lake Ontario and the Bay of Quinte by zebra mussels. Sixty species of zooplankton have been identified in the Bay of Quinte samples, including 41 c1adoceran species, 10 cyc1opoid copepod species and 9 calanoid copepod species. Most common were Bosmina longirostris, Ceriodaphnia lacustris, Chydorus sphaericus, Daphnia galeata mendotae, D. retrocurva, Diaphanosoma birgei, Cyclops vernalis, Diacyclops thomasii, Mesocyclops edax and Tropocyclops extensus. The distribution of zooplankton species in the Bay of Quinte reflects the spatial gradient in

,~ phosphorus concentration and habitat structure (water depth, temperature and thermal structure of the water column) from the shallow, warm, eutropic, upper bay to the deep (32 m), thermally-stratified, mesotrophk lower bay. During the 24-year period oftbis study, the zooplankton community structure changed both with time and along the spatial gradient from the upper to the lower bay. Community composition shifted firstly with the decline in phosphorus concentrations (1979-198112), secondly with the change in the fish community (1982/3-1991), thirdly with the climatic event (cold spring in 1992) caused by the eruption of Mount Pinatubo in 1991 (effects observed only in 1992 (lower bay (C)) or later, 1994 (upper bay (B)), and fourthly with the invasion of zebra mussels (1995-2000). It should be noted that 2000 was also an unusual year and the reasons for these differences are not currently understood. The response of the' zooplankton community to decreases in phosphorus concentration are difficult to distinguish from other effects due to the concurrent changes in the fish community in the 1980s. Changes consistent with decreases in phosphorus were declines in the densities of Chydorus sphaericus, Eubosmina coregoni and Cyclopos vernalis, The zooplankton community in later years in the upper bay (B) was similar to that in the middle bay (HB) in the early years of the study: HB always had lower total phosphorus levels than B. Declines in phosphorus appeared to have relatively more impact in the lower bay (C) than the other sites. Increases in the biomass of piscivores (walleye, large white perch) in the bay in the early 1980s were associated with dramatic changes in the zooplankton community. Total zooplankton biomass, Daphnia biomass, and mean individual length increased with the increase in piscivore biomass. Some zooplankton species increased while others decreased. In total, 33 taxa significantly increased over the 1975-1994 time period, while 18 taxa decreased. Significant increases were found for Daphnia galeata mendotae, and decreases for Leptodora kindtii at all three sampling stations.

2 Zebra mussels (Dreissena) invaded the Bay of Quinte in the mid-1990's; 1995 is considered to be the earliest year with a significant mussel population in the bay. With the arrival of zebra mussels, zooplankton total biomass decreased at all three sites even though zooplankton mean length did not change. This indicates that the decline in

.~ biomass was not related to changes in the level of predation on zooplankton by fish. The declines are most likely related to effects of dreissenids on zooplankton food resources. The ratio of predatory to total zooplankton biomass also decreased at all sites with a decrease in the percentage of cyclopoids in the communities. Thus the relative importance of the herbivorous zooplankton in the pelagic foodweb increased and the relative importance of predatory zooplanktondecreased. Zooplankton community structure was altered and became less stable structure after zebra mussels invaded; also, different species were involved in these changes than those observed with decreases in phosphorus concentrations. Comparisous of community structure between the reference lakes and the upper bay after zebra mussels arrived (1995-2000), indicated that a trend towards a less perturbed state in the upper bay, would have to include reductions in the densities of Eubosmina coregoni, Daphnia retrocurva, Chydorus sphaericus and Daphnia galeata mendotae and increases in Bosmina longirostris, Daphnia pulicaria, total calanoid copepodids, littoral cladocerans, Leptodiaptomus minutus and Diacyclops thomasi. These 10 species/taxon groups accounted for more than 50 % of the dissimilarity between the upper Bay of Quinte (1995-2000) and reference lake zooplankton communities. Potential barriers to the re-establishment of zooplankton communities typifying a less eutrophic Bay of Quinte might include: 1) an imbalanced fish community consisting of excessive biomass of zooplanktivores relative to piscivores, 2) an imbalance in, and/or a depletion offood resources (small-celled phytoplankton species) resulting from the establishment of zebra mussels, and 3) establishment of other exotic, invading species (e.g. Bythotrephes, Cercopagis, Neogobius) with potential to impact directly (by predation) on important zooplankton species. While the reference lake approach used here seems to have been appropriate for evaluation of upper Bay of Quinte zooplankton community rehabilitation, the lakes used in this exercise are not suitable for a similar assessment of the lower bay. Future work on

3 this subject should endeavor to obtain zooplankton data from some other deep-water embayments of the Great Lakes.which could serve as analogues for a less stressed lower Bay of Quinte and thus as restoration targets for lower bay zooplankton community structure. In conclusion, eutrophication, high levels of predation on zooplankton and possibly other related stresses apparently contributed to a perturbed crustacean zooplankton structure in the Bay of Quinte. Prior to major reductions in point-source phosphorus loading in 1977 when the fish community was still dominated by planktivores, zooplankton community structure in the upper bay was most unlike those of reference lakes. Since then, there have been changes that may indicate some recovery; these were manifested at the whole-community evel by increases in total biomass, mean individual size, ratio of large/small Daphnia biomass, and changes in community composition to a structure more similar to that in the reference lakes. With the establishment of zebra mussels in the bay in 1995, zooplankton community structure in the upper and lower bay variability in increased. Decreases in the relative abundance of cyclopoids with the arrival of zebra mussels, the marked decrease in zooplankton biomass and mean size in 2000 and the potential impacts of Cercopagis pengoi and Neogobius melanostoma are cause for concern with regards to the' integrity' of the zooplantkon community. They will need to be evaluated with respect to a final expected 'normal' zooplankton community.

4 Bay of Quinte Remedial Action Plan Assessment of the State of Impairment of Beneficial Uses: II. Zooplankton

Prepared for Fisheries and Oceans Canada and Environment Canada

by

Ora E. Iohannssonl and Ken H. Nicholls2

lGreat Lakes Laboratory for Fisheries and Aquatic Sciences Department of Fisheries and Oceans 867 Lakeshore Rd. Burlington, ON L 7R 4A6

2S-15 Concession 1, RR # 1, Sunderland, Ontario LOC IHO

1 TABLE OF CONTENTS

Page Number

SUMMARy...... :: .... :~...... 4

INTRODUCTION ...... 9

BIOLOGICAL BENEFICIAL USE ASSESSMENT ...... 12

REFERENCE LOCATIONS: RATIONALE AND SELECTION ...... 12

ZOOPLANKTON COMMUNITY STRUCTURE ...... 13 METIIODS ...... 13 Sampling ...... 13 Univariate analyses ...... 14 Multivariate analyses ...... 15 RESULTS ...... 18 Numbers ofSpecies ...... 18 Trends in Densities ...... 19 Apparent Zebra Mussel Effects ...... 21 Whole-Community Changes ...... 22 Comparisons with the Reference Lakes ...... 24 ZOOPLANKTON COMMUNITY FUNCTION ...... 26 METHODS ...... 26 RESULTS ...... 27 Belleville ...... 27 Hay Bay ...... 29 Conway ...... 30 DISCUSSION ...... 31

CONCLUSIONS ...... 37

ACKNOWLEDGMENTS ...... 38

REFERENCES ...... 39

TABLES 1-7 ...... 48-58

FIGURES 1-10 ...... 59-68

2 APPENDIX TABLE 1...... 69-77

APPENDIX TABLE 2 ...... 78-79

APENDIX FIGURES 1-8 ...... 80-87

3 Summary Lake Ontario's Bay of Quinte has been identified as one of 42 Areas of Concern in American and Canadian waters of the Great Lakes for which a Remedial Action Plan (RAP) is required as directed under the bi-national Great Lakes Water Quality Agreement. Most aquatic ecosystem problems in the Bay of Quinte are related to eutrophlc~tion caused by excessive nutrient loading and to degradation ofthe fish community through elimination/depression of top predatory species and invasion of exotic species. These bottom-up and top-down forces have resulted in altered biological communities. Eutrophication impacts zooplankton communities in several ways: it can alter habitat conditions, food quality and feeding, and predation patterns of other interacting biotic components of the aquatic system. Zooplankton community structure is often altered as a result. Similarly, altered fish communities, especially those where planktivorous fish become dominant, reduce individual mean size and grazing capability of the zooplankton community as well as change community structure. Much progress has been made . in the last 25 years in reducing point-source loading of phosphorus in order to rehabilitate the Bay of Quinte. Fish communities resurged with the development of the walleye and lake whitefish populations, and the decline of white perch in the 1980s. Further changes have occurred in the late 1990s with the decline in lake whitefish, redistribution of walleye and resurgence of yellow perch, all associated with the colonization of Lake Ontario and the Bay of Quinte by dreissenid mussels. The major purpose of this report is to assess the Beneficial Use Status of the zooplankton in the Bay of Quinte by examining long-term trends in the crustacean zooplankton community with emphasis on those changes that may be related to rehabilitation of the Bay of Quinte ecosystem and to the recent (1995) establishment of zebra mussels in the bay. A variety of data analysis approaches utilizing both univariate and multivariate methods have been applied to the problem. An integral part of this assessment was the inclusion of zooplankton data from three other reference locations that may serve as analogues for a less perturbed upper Bay of Quinte. It is suggested that the reference location zooplankton communities can thus serve as restoration targets for the upper bay. Comparisons of community structure have been supplemented with comparisons of zooplankton biomass, mean size and ratios of predator/herbivore biomass which

4 reflect patterns of energy flow through the system. This assessment uses a 24-year data series collected under Project Quinte, a multi-agency collaborative study oflong-term change in the Bay of Quinte. Sixty species of crustacean zooplankton have been identified in the Bay of Quinte samples, including 41 cladoceran species, 10 cyclopoid copepod species and 9 calanoid species. Most common were Bosmina longirostris, Ceriodaphnia lacustris, Chydorus sphaericus, Daphnia galeata mendotae, D. retrocurva, Diaphanosoma birgei, Cyclops vernalis, Diacyclops thomasii, Mesocyclops edax and'Tropocyclops extensus. The distribution of zooplankton species in the Bay of Quinte reflects a spatial gradient in eutrophy and habitat structure (water depth, temparature and thermal structure of the water colunm) from the shallow, warm, eutropic, upper bay to the deep (32 m), thermally-stratified, mesotrophic lower bay. A significant change in species richness over time was observed only at station (HB) in the middle of the Bay of Quinte. Here, reductions in species richness averaged 0.23 species/year, with a total reduction in species number of2l % between 1982 and 2000. Very low species numbers (11 and 13) were recorded during 1992 at Stations B and HB, respectively, which likely was related to record low water temperature during that year (although the mechanism is unclear). The zooplankton community structure showed considerable spatial dissimilarity as well as temporal change. Multivariate analyses of species composition illustrated how zooplankton community composition shifted firstly with the decline in phosphorus loading and concentrations (1979-198112), secondly with the change in the fish community (1982/3-1991), thirdly with the climatic event (cold spring in 1992) caused by the eruption of Mount Pinatubo in 1991 (effects observed only in 1992 (Station C) or later, 1994 (Station B)), and fourthly with the invasion of dreisenids (1995-2000). At each of these junctures, the zooplankton community composition changed position in "community" space. At these same junctures changes in community function were also observed. It should be noted that 2000 was also an unusual year and the reasons for these differences are not currently understood. The response of the zooplankton community to decreases in P loading are difficult to distinguish due to changes in the fish community in the 1980s. Changes consistent with decreases in P were declines in the densities of Chydorus sphaericus, Eubosmina coregoni and Cyclopos vernalis. Cluster analysis also indicated that the zooplankton community in later years

5 at Station B was similar to that at Station HB in the early years of the study: HB always had lower total phosphorus levels than Station B. Declines in P-loading appeared to have relatively more impact at Station C than the other sites. Comparisons of zooplankton community structure between the pre-phosphorus control years of 1975-76 and the more recent pre- and post

.~ Dreissena years revealed that the differences were most significant at Station C and least significant at Station B. Increases in the biomass of piscivonis (walleye, large white perch) in the bay in the early 1980s were associated with dramatic changes in the zooplankton community. Total zooplankton biomass, Daphnia biomass, and mean individual length increased with the increase in piscivore biomass. Some zooplankton species increased while others decreased. In total, 33 taxa significantly increased over the 1975-1994 time period, while 18 taxa decreased. Significant increases were found for Daphnia galeata mendotae, and decreases for Leptodora kindtii at all three sampling stations. Other trends included increased densities of benthic cladocera, Bosmina longirostris, total Daphnia sp. and Holopedium gibberum in the middle and lower bay, but not in the upper bay. Daphnia pulicaria, Skistodiaptomus oregonensis, benthic copepods, total adult calanoids and Mesocyclops edax all increased in the upper and middle bay, but not in the lower bay. Chydorus sphaericus, and total calanoid copepodids declined in the middle and lower bay, but not the upper bay, and Diaphanosoma birgei decreased in the upper and middle bay over the 1975-1994 period. Zebra mussels (Dreissena) invaded the Bay of Quinte in the mid-1990's; 1995 is considered to be the earliest year of a significant Dreissena popUlation in the bay. With the arrival of dreissenids, zooplankton total biomass decreased at all three sites even though zooplankton mean length did not change. This indicates that the decline in biomass was not related to changes in the level of predation on zooplankton by fish. The declines are most likely related to effects of dreissenids on food resources. The ratio of predatory to total zooplankton biomass also decreased at all sites with a decrease in the percentage of cyclopoids in the communities. Thus the relative importance of the "grazer pathway" in the pelagic foodweb increased and the relative importance of the microbial loop, which is dependent on predation by zooplankton to transfer energy up the foodweb to fish from ciliates and rotifers, decreased.

6 In tenns of specific species effects - only two crustacean zooplankton species or taxon groups at Station B, three at Station HB and four at Station C showed significant differences between pre- and post Dreissena 6-year time periods (1989-1994 vs 1995-2000); however it has not been possible to detennine conclusively that the observed changes in any of these taxa were

.~ caused by the establishment of Dreissena. The best case for a Dreissena effect might perhaps be made for those zooplankton taxa that showed a significant change in the 6-year pre- and post Dreissena comparisons, following the absence of a significant longer tenn trend in the 1975- 1994 data series. Taxa fitting this condition include declines in Chydorus sphaericus at Station B (-67 %), Daphnia pulicaria at Station C (-94 %), total cyclopoid copepodids at Stations B (-67 %) and C (-57 %), and increases of 317 and 186 %, respectively, at Stations HB and C, in total calanoid nauplii. The multivariate data analysis revealed an altered and less stable community structure after dreisenids invaded; also, different species were involved in these changes than those observed with decreases in P-loading. Comparisons of community structure between the reference lakes and the upper bay after dreissenid arrived (1995-2000), indicated that a trend towards a less perturbed state in the upper bay, would have to include reductions in the densities of Eubosmina coregoni, Daphnia retrocurva, Chydorus sphaericus and Daphnia galeata mendotae and increases in Bosmina longirostris, Daphnia pulicaria, total calanoid copepodids, littoral cladocerans, Leptodiaptomus minutus and Diacyclops thomasi. These 10 species/taxon groups accounted for more than 50 % of the dissimilarity between the upper Bay of Quinte (1995-2000) and reference lake zooplankton communities. Potential barriers to the re-establishment of zooplankton communities typifying a less eutrophic Bay of Quinte might include: 1) an imbalanced fish community consisting of excessive biomass of zooplanktivOIes relative to piscivores" 2) an imbalance in, and/or a depletion offood resources (small-celled phytoplankton species) resulting from the establishment of Dreissena, and 3) establishment of other exotic, invading species (e.g. Bythotrephes, Cercopagis, Neogobius) with potential to impact directly (by predation) on important zooplankton species. While the reference lake approach used here seems to have been appropriate for evaluation of upper Bay of Quinte zooplankton community rehabilitation, the lakes used in this

7 exercise are not suitable for a similar assessment of the lower bay. Future work on this subject should endeavor to obtain zooplankton data from some other deep-water embayments of the Great Lakes (e.g. Twelve-Mile Bay of Georgian Bay and South Bay on Manitoulin Island) that could serve as analogues for a less stressed lower Bay of Quinte and thus as restoration targets

.~ for lower bay zooplankton community structure in the same way that the upstream Trent-Severn Waterway locations have served for the upper bay. In conclusion, eutrophication, high Jt;vels of planktivory and possibly other related stresses apparently contributed to a perturbed crustacean zooplankton structure in the Bay of Quinte. Prior to major reductions in point-source phosphorus loading in 1977 when the fish community was still dominated by planktivores, zooplankton community structure in the upper bay was most unlike those of reference (target) lakes. Since then, however, there have been changes that may indicate some recovery; these were manifested at the whole-communityOlevel by increases in total biomass, mean individual size, ratio of large/small Daphnia biomass, decreases in predatory ratio, and changes in community composition to a structure more similar to that represented in the reference lakes. Increased inter-annual variability in zooplankton community structure in the upper and lower bay was associated with the establishment of zebra mussels in the bay in 1995. Decreases in the relative abundance of cyclopoids with the arrival of dreissenids, the marked decrease in zooplankton biomass and mean size in 2000 and the potential impacts of Cercopagis pengoi and Neogobius melanostoma are cause for concern with regards to the 'integrity' of the zooplantkon community. They will need to be evaluated with respect to a final expected 'normal' zooplankton community.

8 Introduction In 1985, the International Joint Connnission identified Lake Ontario's Bay of Quinte as one of 42 Areas of Concern (AOC) in American and Canadian waters of the Great Lakes. Under Annex 2 of the amended (1987) bi-national Great Lakes WaterQuality Agreement (GLWQA), specific water quality issues and ecosystem impairments in each of these AOCs were to be addressed under Remedial Action Plans (RAPs). There are three main reporting requirements for a RAP. Stage 1 Reports identifY the environmental/ecological issues; Stage 2 Reports outline plans for remediation, and Stage 3 Reports document the recovery and restoration of beneficial uses following remediation. At present, the Bay of Quinte RAP is in an early phase of Stage 3. Most aquatic ecosystem problems in the Bay of Quinte of Lake Ontario (Fig. 1) are related to eutrophication caused by excessive nutrient loading, believed to have begun with the deforestation of the Bay of Quinte watershed in the early 1800s (Warwick 1980, Stoermer et al. _ 1985). Phosphorus (P) loading from sewage treatment plants (STPs) further aggravated the Bay of Quinte ecosystem beginning about the middle ofthe last century (Minns et al.1986b). More recently, P loading from these sources has declined dramatically as a result of improved STP performance and implementation of state-of-the-art P removal technology. By the beginning of this new century, phosphorus concentrations at major STP sources discharging to the Bay of Quinte were typically in the range of 0.1-0.2 mg/L compared to levels in the 5-10 mg/L range in the late 1960s. Total P loading to the bay from STPs had declined by over 90% between the early 1970s and the early 2000s (White 2001). In addition, the Bay of Quinte RAP Stage 2 Report advocated further control of mainly non-point phosphorus sources and outlined 14 specific remedial actions required to achieve these reductions from a number of urban and agricultural sources (Bay of Quinte RAP, 1993). Anthropogenic impacts on the integrity of the biological connnunity are also mediated through changes in the structure of the fish connnunity. People have systematically fished down the large predatory fish in the Lake OntariolBay of Quinte system since the mid-1800s and allowed the introduction of a variety of exotic fish species (Christie, 1974). Attempts at remediation of the fish community through the introduction of salmonids and control of sea lamprey, and the arrival of exotics, such as dreissenid mussels and round gobies, have continued

9 to change the fish community up to the present time (2002) (O'Gorman and Stewart 1999; Mills et al. submitted). In the 1970s prior to P-control, the Bay of Quinte lacked a strong piscivore population - the community was composed of a large number of small-bodied, or stunted, fish with short life spans and high reproductive capacity (Hurley and <;hristie 1977), mainly white perch (Morone americana) and alewife (Alosa pseudoharengus). Phosphorus control came on line in 1977. In the winter of 1977, the alewife population suffered a severe over-winter mortality (0' Gorman and Schneider 1986). in 1978, the adult white perch population collapsed, again due to severe over-winter mortality associated with the exceptionally cold spring (Minns and Hurley 1986). The white perch population had been declining since 1972. In 1977, and particularly 1978, the renmant walleye population produced large cohorts which survived their first summer - perhaps due to decreased predation by white perch and alewife. The dramatic loss of white perch and production of walleye changed the structure ofthe fish community (Hurley 1986). Although the white perch population started to recover, the trend stopped in 1981 as the abundance of larger walleye increased and were able to control white perch abundance. Walleye also depressed the alewife population in the upper bay. White perch growth was faster at these low population densities and individuals more rapidly reached sizes where they became piscivorous. Thus the fish community, particularly in the upper bay, became more piscivore­ dominated and these piscivores ate alewife, smelt, white perch and yellow perch - all the species which were abundant in the pre-P control period (Hurley 1986). Alewife populations declined in Lake Ontario due to predation from the increasing populations of stocked sahnonids, starting in the mid-1980s (O'Gormanand Stewart 1999). This decline was important in shifting the fish community in the lower bay towards a more piscivore-dominated community. Shifts in the fish community are important to the functioning of the zooplankton community because they can alter zooplankton mean size, total biomass, productivity, and the relative importance of the microbial loop and grazing food chains. The former funnels energy to fish through rotifers and predacious zooplankton; such as cyclopoids, while the later funnels energy to fish directly from algae to herbivorous zooplankton species; such as most cladocerans and calanoids. The latter is more energy-efficient as material passes through fewer trophic levels (Sprules 1980). The establishment of zebra mussels (Dreissena spp.) by 1995 may also have

10 influenced the Bay of Quinte zooplankton community. Zebra mussel larval stages (veligers) are planktonic and occupy the same habitat as crustacean zooplankton and consume the same food (bacteria and phytoplankton) (Sprung 1993). Adults colonize rocks and other hard substrates and filter the overlying water, directly impacting immature crustace~s (e.g. copepod nauplii (Shevtsova et al. 1986 in MacIsaac et al. 1995) and indirectly affecting all crustaceans by decreasing their food supply (algae, rotifers) in the water column (Ten Winkel and Davids 1982, Cotner et al. 1995, Lavrentyev et al. 1995). Furthermore, tlieir colonization has altered the fish community structure. Walleye distribution has changed with larger walleye leaving the upper bay as water clarity increased due to zebra mussel filtration (Stewart et al. 2000). Yellow perch, small­ mouthed bass, and pan-fish populations have increased (Stewart et al. 2000). These changes are shifting the balance of piscivores and planktivores towards a more planktivore-dominated community again. The Bay of Quinte RAP Stage 1 Report identified impairment of 10 of the 14 beneficial use categories set out by the Annex 2 of the GLWQA. Among these was degradation of phytoplankton and zooplankton populations (no. xiii). Eutrophication impacts zooplankton communities in several ways. One typical manifestation of eutrophication is the proliferation and change in species composition of phytoplankton leading to less desirable food supply for zooplankton and decreased efficiency in food chain function. The proliferation of large colonial diatoms and other undesirable blue-green algae (cyanobacteria), the loss of macrophytes in littoral zones, the increased dissolved oxygen deficits in deep-water zones, the degradation of fish spawning shoals by accumulation of organic detritus and the decreased water transparency were all associated with eutrophication of the Bay of Quinte (Minns et al. 1986a). These alterations impact directly (habitat change) and indirectly (fish community changes resulting in altered predation patterns) on zooplankton community composition and function. The major purpose of this report is to identifY long-term trends in major species of crustacean zooplankton. Specifically, changes that may have been related to changes in fish compostion, the establishment of zebra mussels and other habitat changes associated with eutrophication control (e.g. improved water clarity, expansion of macrophytes) are detailed. Also included are some data from three other reference locations in southern Ontario were

11 zooplankton communities are deemed to be less severely impacted and where zooplankton community structure might help to define a restoration target for the Bay of Quinte. Modern methods of multivariate data analysis are applied to compare these communities and to help evaluate change over time. Throughout this discussion, the term :estoration is used even though it is clearly not the intention to restore the Bay of Quinte ecosystem to original pre-European settler conditions. The intention in the Bay of Quinte RAP is to achieve an ecosystem condition that is characteristic of a less severely impacted state. In this context, the term enjuvenation (sensu Christie et al. 1987) is useful, but because it has not been widely adopted in the RAP context, it has not been used here.

Biological Beneficial Use Assessment According to the Great Lakes Water Quality Agreement (DC 1987), Beneficial Use hnpairments (BUA) result from the loss of chemical, physical or biological integrity. Biological integrity is 'the capability' of the ecosystem' of supporting and maintaining a balanced, integrated, adaptive community of organisms having a species composition, diversity and functional organization comparable to that of natural habitat in the region' (Karr and Dudley 1981). !fa system has biological integrity it will also be healthy (Karr 1995, Callicott 1995). Ecosystem health is defined more on the basis of function, that is, the movement of matter and energy through the trophic food-web (Callicott 1995). Assessment of the zooplankton 'beneficial use' will include consideration of both structural and functional characteristics of the community.

Reference Locations: Rationale and Selection The listingldelisting criteria set out by the liC (International Joint Commission 1989) specifY that objectives for attainment of restored beneficial uses can result from comparisons with un-impacted reference locations or from restoration to some acceptable historical pre-impact (or lower impact) ecosystem condition. The reference condition approach (cfReynoldson et al. 1997, as applied to benthos) has been pursued here, but employs different methods to achieve its objectives. Comparisons of community structure have been supplemented with comparisons of zooplankton biomass, mean size and ratios of predatorlherbivore biomass which reflect patterns of energy flow through the system.

12 A fundamental objective of the Bay of Quinte RAP is to reduce phosphorus concentrations in the upper bay to a May-October mean of about 30 J.1g/L. Although no explicit restoration targets exist for Bay of Quinte zooplankton (Bay of Quinte RAP 1993), there are general features of a rehabilitated upper bay ecosystem that have been described and can help ,-' - .j serve to identify useful reference locations elsewhere in southern Ontario (i.e. of similar climate). These objectives include moderate densities of mixed-species stands of rooted macrophytes, a diverse community of warm-water fish, including at least one dominant top piscivore (e.g. northern pike, muskellunge or walleye) and relatively clear water. It is inferred that aquatic ecosystems possessing such features will also harbor more desirable zooplankton communities than those existing in the upper Bay of Quinte during the 1970s (Cooley et al. 1986), when the fish community was grossly imbalanced by its domination by alewife and white perch (Hurley and Christie 1977), and macrophytes were sparsely distributed and oflow biomass (Crowder and Bristow 1986). It is also important that such reference ecosystems be free of zebra mussels so that the impacts of these invading species can be separated from the other eutrophication-related stresses contributing to the degraded state ofthe upper Bay of Quinte. Zooplankton data from three reference locations (Table I) over two pre-zebra mussel years (1987-1988) were selected for comparisons with those of the Bay of Quinte. All three of these reference locations have diverse warm-water fish communities (Breton 2000; Leslie and Timmins 1994; McMurtry et al. 1997).

Zooplankton Community Structure

Methods

Sampling This analysis uses data collected over a 26 year period (24 years of data) under Project Quinte, a multi-agency collaborative study of long-term change in the Bay of Quinte (Minns et al. 1986a). Description of methods for zooplankton sampling and analyses are in Cooley et al. (1986) and Bowen et al. (2001). Briefly, samples were obtained from three main locations in the Bay of Quinte: Belleville (B), Hay Bay (HB) and Conway (C) (Fig. 1) with a 41-L plexiglass

13 trap fitted with 75-f.Ull mesh net in the filtration bucket. Samples were collected at several depths to allow for production of a composited sample representative of the water column. Sampling was weekly during the May-October periods of 1975-1981, and biweekly during 1982-2000 except in 1978 and 1979, when no samples were collected. For all~years, time-weighted seasonal means representing the May I - October 6 time period were calculated for each zooplankton species or grouping (Appendix 1).

Univariate analyses The seasonal means were organized in a spreadsheet matrix for all recorded taxa, all of which were retained for species richness analysis (defined simply as numbers of species occurring in a given year). Trend analysis was run on all taxa except those occurring only a few times in the 24-year record and was based on non-parametric sign tests. Sign test protocol involves comparing the seasonal mean for each taxon with all succeeding seasonal means, in tum. For each comparison, a negative sign was assigned if the first mean in the pair was higher than the second (succeeding) mean, and a positive sign was assigned if it was lower; no sign was assigned if the two values were tied. Zero values were not included in the comparisons. Increasing trends were thus characterized by a sign total which was positive, and decreasing trends, by a negative sign total. The sign test null hypothesis was a sign total not significantly different from zero (i.e. theoretically, zero median). Statistical significance was assessed by referral to a table of probabilities (x 2, because these are two-tailed tests - trends can be either increasing or decreasing) or to computer generated probabilities (Knodt 1999) for a normal distribution of sign totals after conversion to z-scores which included a continuity correction for data sets where N (number of paired years) > 25 (Siegel 1956). Where N < 25, the number of either positive or negative signs in the smaller of the two categories was referred to a table of binomial probabilities [Table D of Siegel (1956)], again doubling the listed probabilities because ofthe two-tailed nature of these analyses. For 10 of these sign tests for which N > 25, trends were also assessed by bootstrapping (10,000 resamplings; Peladeau and Lacouture 1993), where the 95 % confidence intervals of the bootstrapped mean were compared with the null hypothesis (no trend: sign mean = zero) to

14 determine statistical significance (Appendix Fig. 2). When it was apparent that the two methods (i.e. (i) conversion of signs to a z-score and referral to probabilities in a normal distribution, and (ii) bootstrapping the distribution of the mean) were in complete agreement, the bootstrapping approach was discontinued. Sign tests were run on all zooplankton taxa, except those of very infrequent occurrence, for two time blocks: the whole period of investigation, 1976-2000, and for just the pre-zebra mussel period, 1976-1994 to provide an indfrect measure of possible zebra mussel effects. More direct measures of apparent zebra mussel effects were examined by comparing the median densities of all important crustacean zooplantkon taxa in 6-year pre- and post Dreissena time blocks (1989-1994 vs 1995-2000) using non-parametric Mann-Whitney U-tests in CoStat (CoHort Software1995).

Multivariate analyses For comparative purposes, crustacean zooplankton data were obtained for reference lakes in Ontario (see below). These data were selected in part for their compatibility (similar sampling and analysis methods). However, some minor differences in the reporting of a few taxa and more importantly, the need to reduce the numbers of taxa to more easily interpretable units necessitated some changes in the master zooplankton data file used for multivariate analyses. In particular, some data reduction was done for rare taxa and for others that could be grouped into niche descriptors (e.g. benthic Cladocera) before multivariate analysis. These changes are summarized below: 1. Four new categories were created: benthic copepods, benthic cladocerans, littoral copepods, and littoral cladocerans. (a) Benthic copepods include Eucyclops agilislserrulatus and E. speratuslelegans. (b) Benthic cladocerans include all Alona species, Eurycercus spp. and flyocryptus spinifor. (c) Littoral copepods include Macrocyclops albidis, Paracyclops fimbriatus poppei and Orthocyclops modestus. (d) Littoral c1adocerans includes Pleuroxus denticulatus, Acroperus harpae,

15 Simocephalus serrulatus, S. vetulus, Diaphanosoma brachyuran, all Ceriodaphnia spp., Ophryoxus gracilis, Camptocercus rectirostris, Leydigia quadrangularis, Latona setifera and Sida crystallina. 2. The following taxa were removed owing to sparse occurrence: Cyclops strenuus, Eubosmina

.~ tubicen, Bythotrephes longimanus, Pleuroxus sp., P. procurvus, Rynchatalona spp., Ergasilis spp., Cyclops varicans rubellus, Dreissena veligers, and Cercopagis pengoi. [note that Dreissena veligers were common in the Bay of Quinte after 1994, but they were removed from this file because they are not an independent variable in the multivariate analysis (we want to know ifthe rest of the zooplankton community changed after Dreissena establishment)] 3. Eubosmina longispina was included in Bosmina longirostris. 4. Chydorus sphaericus includes C. globosa. 5. Harpacticoids (sometimes recorded in B ofQ samples, but never recorded (no code available) for other reference locations) were deleted. 6. Copepodid stages of Episehura laeustris and Limnoealanus maerurus were included in a new group, total calanoid copepodids. 7. Naupliar stages of Limnoealanus maerurus were combined with calanoid nauplii under the new group "total calanoid nauplii". 8. Daphnia pulex combined with D. puliearia. 9. Tropocyclops prasinus mexieanus was combined with T. extensus because these are different names for the same species. Multivariate analyses were used to help identify spatial (among the three sampling stations) and temporal (1976-2000) patterns in community structure. Methods advocated by Clark (1993, 1999) utilizing the Bray-Curtis similarity measure on 4th root-transformed zooplankton density data, cluster analysis by a group averaging algorithm, and ordination by non­ metric multidimensional scaling (NMDS) were used. Each sampling location-year was designated as a sampling unit (SU), each of which represented a May 1 - October 6 seasonal mean, as described above. For example, the Bay of Quinte data contained a total of72 SUs (3 stations x 24 years). Similarly, for the reference lakes, a total of 12 SUs were generated (two

16 sampling stations from each location over two years (1987 and 1988) as follows: Penetang Bay­ Stations PI and P3; Lake Simcoe - Stations Cl and C6; Sturgeon Lake - Stations S10 and SII. These were initially grouped into one data set for preliminary global analyses, the purpose of which was to detect patterns among all Bay of Quinte and reference locations and between all ., available years. Several smaller sub-sets of SUs were analyzed in order to examine in more detail differences between the important time blocks (e.g. pre- and post zebra mussels for Quinte alone). Note that these reference locations are considered suitable for the upper Bay of Quinte, but not for the lower bay, where water depth, deep-water temperature, phosphorus concentrations and other trophic status indicators differ greatly from the upper bay. Data from other Ontario locations which may be more suitable as reference comparisons for the lower Bay of Quinte (e.g. South Bay of Manitoulin Island, Twelve-Mile Bay of Georgian Bay), should be obtained and applied to the multivariate analytical protocol used here. The multivariate methods used here are well suited for multi-year and multi-location studies where an important objective is to gauge the significance of shifts in zooplankton community composition over time and space. The attaimnent of, or movement towards, more desirable community structure is easily visualized in the clustering and ordination displays. A Bay of Quinte zooplankton community that is responding to water quality and other ecosystem improvements will demonstrate increasing resemblance to those zooplankton communities characterizing the reference locations. Qualitatively, this is visualized in an NMDS ordination wherein the distances between SUs in the ordination plane are directly related to community similarities (e.g. SUs that moved closer together over time in the NMDS ordination became more similar in their community composition). Quantitative assessments of changes in community structure were made in the context of within versus between site comparisons of community similarity (i.e. are such changes statistically significant?) and utilized the ANOSIM protocol of Clark and Green (1988) [see also Clarke (1999)]. Briefly, a test statistic, R, was computed that reflects the differences in rank similarities between sites contrasted with the differences among sites (or replicates at a site). R ranges

between -1 and +1. R = +1 only if all replicates within sites are more similar to each other than to

any other replicate from any other site. R = 0 if Ho is true (i.e. there is no difference in community

17 structure between sites). The test for significant difference from 0, involved Mantel-type permutation/randomization tests whereby R was calculated a large number of times as the SU labels were randomly re-assigned (here, 10,000 times or if <1 0,000, the maximum number of permutations possible given the upper limits imposed by the number of replicates in the groups

.~ under comparison). As a result, a frequency distribution of R values was generated, to which the original calculated R was compared for probability inference. The taxa contributing most to significantly different groups of SU' s were determined by the SIMPER routine in PRIMER (Carr 1997) as discussed in Clarke (1993, 1999). Briefly, the contribution of each taxon to the average dissimilarity between all pairs of inter-group SU's 0 - - was calculated. Many pairs of samples contribute to 0, and so, if for a particular taxon, i, 0; is large and its standard deviation (SD) is low (i.e. o;lSD(o) is large), then this taxon is an important [and consistent, because of the low SD(o)1 contributor to the dissimilarity between the groups. Throughout the multivariate approach described above, different years at reference locations were all treated as within-site replicates. Similarly, different years within each of the time intervals under examination were treated as replicates. For example, the extent of the departure of the 1996-2000 post Dreissena zooplankton composition from its pre-Dreissena state was addressed in terms of the difference between the overall dissimilarity of the pre-Dreissena years (replicates) and that of the post Dreissena years (replicates), wherein the inter-year zooplankton community dissimilarities were not specifically evaluated (except in the context of

the between vs within calculation of R).

Results

Numbers ofSpecies Sixty species of crustacean zooplankton have been identified in the Bay of Quinte samples, including 41 cladoceran species, 10 cyclopoid copepod species and 9 calanoid species (Table 2). The much lower diversity of copepod species relative to cladoceran species in the Bay of Quinte is consistent with the findings from the three reference lakes: Sturgeon Lake (Standke 1994), Lake Simcoe (Nicholls and Tudorancea 2001a, 2001b), and Penetang Bay (Gemza 1995)

18 as well as other north-temperate lakes (patalas 1990, Arnott et al. 1998, Korovchinsky 2001). Several species were very common, occurring virtually every year at all three stations: Bosmina longirostris, Ceriodaphnia lacustris, Chydorus sphaericus, Daphnia galeata mendotae, Daphnia retrocurva, Diaphanosoma birgei, Cyclops vernalis, Diqcyclops thomasii, Mesocyclops edax and Tropocyclops extensus (Table 2). Other patterns of occurrence include several species with decreased frequency of occurrence from the upper to the lower bay. These included some Alona species, Eurycercus lamellatus, flyocryptus spinifer and some Eucyclops and Ergasilis species (Table 2). In contrast, Daphnia longiremis,Polyphemus pediculus, Eurytemora ajfinis, Limnocalanus macrurus, and several species of Leptodiaptomus and Skistodiaptomus were more frequently encountered in the lower bay (Station C) than the middle (Station HB) and upper (Station B) bay 10cation(Table 2). More species were recorded at all three sampling stations during the first five years of the program than during subsequent years (Fig. 2), but this was likely the result of about twice as many samples having been collected and analyzed during the early years. However, for just the period 1982-2000 (when inter-aunual sampling and analyses were at about equal frequency), a significant decreasing trend was detected only for Station HB (non-parametric sign tests; P =

0.805, P < 0.0001 and P = 0.625 at Stations B, HB and C, respectively). At Station HB, the reduction in species richness averaged 0.23 species/year, with a total reduction in species number of21 % between 1982 and 2000. Very low species numbers (11 and 13) were recorded during 1992 at Stations Band HB, respectively (Fig. 2). The number of cladoceran species was about two times greater than the number of copepod species at each of the three stations. In the lower bay (Station C), the numbers of calanoid copepods was greater than the number of cyclopoid species during most years, while the reverse was true at Station B in the upper bay (Fig. 2). On balance, the total number of species recorded each year at all three locations (all groups combined) was about equal, averaging about 15-20 during the recent past (Fig. 2).

Trends in Densities More taxa increased during the period of the study than decreased. In total, 36 and 33 taxa

19 significantly increased over the 1975-2000 and 1975-1994 time periods, while 24 and 18 taxa decreased over these time periods (Fig. 3; Appendix Table 1). Responses at all three stations were consistent for a surprisingly large number of taxa, given the great differences in habitat (depth, water clarity and temperature) at these stations. For example, inc~eased densities at all three stations were found for Daphnia galeata mendotae for both time periods, for total calanoid. nauplii, total cyclopoid nauplii and for Skistodiaptomus oregonensis for the 1975-2000 time period; decreased densities at all three stations during both time periods were found for Leptodora kindtii, and for the 1975-2000 period for Chydorus sphaericus, Eubosmina coregoni, Cyclops vernalis, total adult cyclopoids and total cyclopoid copepodids (Fig. 3; Appendix Table 1). Increases in some taxa were often restricted to just two adjacent stations. The middle bay station (HB) was apparently caught in the middle between upper and lower trends. Station HB trends were the same as the upper bay (B) response for about the same number oftaxa as found for concurrent increases at the middle and lower bay stations for other taxa. For example, benthic Cladocera, littoral Cladocera, Bosmina longirostris, Daphnia pulicaria, total Daphnia species and Holopedium gibberum all increased in the middle and lower bay during 1975-2000 (but not in the upper bay), while Leptodiaptomus minutus, benthic copepods and Mesocyclops edax all increased in the upper and middle bay, but not in the lower bay during 1975-2000. Similarly, four taxa (benthic Cladocera, Bosmina longirostris, total Daphnia species and Holopedium gibberum) all increased during the1975-l994 period in the middle and lower bay, while five taxa (Daphnia pulicaria, Skistodiaptomus oregonensis, total adult calanoids, benthic copepods and Mesocyclops edax) increased at the middle and upper bay, but not at the lower bay station in the 1975-1994 (pre-zebra mussel) period (Fig. 3; Appendix Table 1). In addition to the trends described above, many different long-term patterns were evident for several taxa. Many achieved their highest densities during the middle years of the study. These included littoral and benthic cladocerans, Daphnia pulicaria, Leptodiaptomus siciloides and Cyclops vernalis at Stations Band HB (Appendix Figs 3a, 3b, 3d, 6c, 8b), Bosmina longirostris at Station B (for which a seasonal mean exceeding 320,0001m3 was recorded for 1991 (Appendix Fig. 4a), total cyclopoid copepodids at Station HB (Appendix Fig. 7d), and total cyclopoid copepodids, Mesocyclops edax and Tropocyclops extensus at all stations (Appendix Figs 7d, 8c,

20 8d). With the exception of some Daphnia species, most zooplankton species had very low seasonal mean densities during 1992 (Appendix Figs 1-8); some of these (cyclopoid copepods in particular) took more than one year to recover. The other universally low-density year was 2000 (Appendix Figs 1-8).

Apparent Zebra Mussel Effects Zebra mussels (Dreissena spp.) became well established by 1995. Dreissena veliger larvae peaked in 1997 in the upper and lower bay, where May-October means of more than 137,000/ml at Station B and 43,000/ml at Station C were measured (Figs 4a, 4c). Densities at Station HB did not peak until 2000 (at about 58,000/ml; Fig. 4b). Only two species or taxon groups at Station B, three at Station HB and four at Station C showed significant differences between the pre- and post Dreissena 6-year time periods (Appendix Table 2, Figs 4d-41). Four taxa had similar trends at two of the three stations: Chydorus sphaericus declined 67 % at Station B (Fig. 4d) and 44 % at Station HB (Fig. 4e); Holopedium gibberum increased at Stations HB and C by 280 % and 200 %, respectively (Figs 4h, 4i); total cyclopoid copepodids declined 61 % and 57% at Stations B and C (Figs 4g, 41); total calanoid nauplii increased at Stations HB by 317 % (Fig. 4k) and at Station C by 186 % (Fig. 4j). The only other significant change correlated in time with the establishment of zebra mussels was a decline in Daphnia pulicaria of 94 % at Station C (Fig. 4 f). It has not been possible to determine conclusively that any ofthe above changes were caused by the establishment of Dreissena. In fact, in the case of the increases in Holopedium gibberum at both Stations HB and C, this is most likely not so, because a very significant increase in this species was detected for the entire pre-Dreissena period of 1975-1994 at both of these stations (Appendix Table I). The further increase following the Dreissena establishment could simply have reflected a continuation ofthe pre-Dreissena longer-term trends and may therefore have been quite independent of the establishment of Dreissena. A case for a Dreissena effect might perhaps be made for those taxa that showed a significant change in the 6-year pre- and post Dreissena comparisons, providing there was no significant longer term trend in the 1975-1994 data series. Taxa fitting this condition include Chydoricus sphaericus at Station B, Daphnia pulicaria at Station C, total cyclopoid copepodids at

21 Stations B and C, and total calanoid nauplii at Stations HB and C. The strongest case for a Dreissena effect should be made for those taxa that, following 1994, reversed a trend set during the pre-Dreissena period of 1975-1994; however there were no Bay of Quinte zooplankton taxa for which this condition applied.

Whole-Community Changes At the multivariate level of data analysis, strong indications of altered zooplankton commuuity structure during the most recent years is an indication of a possible zebra mussel effect. Concurrently, at least at Stations B and C, inter-annual variability in commuuity structure increased greatly after 1994 (Fig. 5). Pictorially, this was most evident in the ordinations, where the inter-SU distances in recent years were often very great (lower portions of Figs 5a and 5c). The 1992 SU was also clearly dissimilar from others at Stations Band HB, and included 1993 at Station C, where the separation of the pre-phosphorus control years, 1975 and 1976, from the other SUs was the greatest of the three Bay of Quinte stations (Fig. 5). The stress values of all three ordinations were relatively low (0.03 - 0.06) and indicate that the two dimensional ordinations did a reasonably good job of placing the SUs into two dimensional space, such that inter-SU distance reflected inter-SU commuuity dissimilarity. [NOTE: the NMDS ordination algorithm is best-fit iterative process that seeks to configure multiple SUs (based on rank-order) in two-dimensional space such that inter-SU distances achieve the highest degree of correlation (i.e. lowest stress) with the measured paired SU dissimilarities). However, it should be pointed out that in attempting to display the inter-SU commuuity similarities in these two-dimensional ordinations, some degree of reality has been lost, especially with the Station B data where the ordination stress was 0.16. Most of this higher stress was likely as a result of attempting to fit the 92 and 00 SUs into the two-dimensional framework of the remaining stations. The cluster analysis revealed that these two SUs (92 and 00) were very similar at Station B (Fig. 5a, upper portion), but their wide separation in the ordination field did not reflect this. Ordination stress was lowered to 0.01 in a three-dimensional ordination of the Station B zooplankton commuuity similarities, but this did not enhance the interpretive value of the ordination owing to the difficulty in visualizing so many (24) inter-SU distances in a single three-dimensional plot. Clearly, the cluster analysis dendrograms

22 need to be scrutinized along with the ordinations in any attempts to identify patterns in the data. Despite some apparent outliers (i.e. the 92 and 00 Station B SUs, the 92 SU at Station lIB and the 92 and 93 SUs at Station C), the pattern that emerged from the multivariate analyses at all three Bay of Quinte stations was one that suggested a time-trend with the greatest differences in

.~ zooplankton community structure existing between the pre-phosphorus control period and the post Dreissena zooplankton communities of the late 1990s.(the inter-SU distances in the ordinations are greatest between the groups of SUs enclosed within the dashed lines). In addition, the ANOSIM analyses revealed that the pre- and post Dreissena differences in zooplankton community structure at all three stations (and whether or not the 1992 SU was omitted) were unlikely to have resulted from chance alone (Table 3). Similarly, the differences in zooplankton community structure between the pre-phosphorus control years of 1975-76 and the more recent pre- and post Dreissena years were most significant at Station C and least significant at Station B, where only the pre-P control vs pre-Dreissena comparison (after omission ofthe 1992 SU - Part II of Table 3) revealed significant differences in zooplankton community structure. The species contributing most to the difference between the pre-P control and pre- and . post Dreissena zooplankton communities included both abundant and less common taxa and are summarized in detail here (Tables 4 and 5) for Station C only (the analyses were also run for the other two stations, but will not be discussed in detail here). Twenty-five taxa (from cyclopoid nauplii down to Mesoeyclops edax in Table 4) contributed 90 % ofthe difference in similarity between the two groups of SUs (pre-P control vs pre-Dreissena). The remaining seven taxa

contributed the ~emaining 10 % of the difference. More than 50 % ofthe difference in zooplankton community similarity between these two groups was attributable to increased densities of cyclopoid nauplii, Daphnia galeata mendotae, Daphnia retroeurva, Bosmina longirostris, cyclopoid copepodids, Eubosmina eoregoni and total calanoid nauplii and decreases in Daphnia longiremis, littoral cladocerans and Limnoealanus maerurus. (Table 4). A very different group of zooplankton taxa were responsible for the difference in community structure between the pre- and post Dreissena time periods at Station C. In this case, the difference was attributable to increased densities of Chydorus sphaericus, total calanoid nauplii and littoral cladocerans, and decreases in Bosmina longirostris, cyclopoid copepodids, Eubosmina coregoni,

23 Tropocyclops extensus, Leptodiaptomus siciloidesand Daphnia pulex. These nine taxa accounted for 50 % of the difference in community structure pre- and post Dreissena establislunent at Station C (Table 5).

Comparisons with the Reference Lakes When the reference lakes were incorporated into the Bay of Quinte set of 72 SUs, the total number of SUs under the larger analysis increased to 86. Important patterns emerged from this larger analysis; for the most part, SUs within stations tended to group together, suggesting that the changes over time within stations were not so great to obscure the distinctiveness ofthe zooplankton community structures at each of the three Bay of Quinte stations, especially at Station C (cluster g in Fig. 6). There were exceptions, however. The early years at Station HB were more like the early-to-middle years at Station B (Fig. 6, cluster el), and the later years at Station B were more like the middle-to-Iater years at Station HB (Fig. 6, cluster f). Generally then, the zooplankton communities at Station B became more like those characterizing Station HB during the period of the mid-1980s through the late 1990s. A separate group of four SUs . comprising B-93, B-95, HB-93 and HB-94 (Fig. 6, cluster e2) had zooplankton communities that were more similar amongst themselves than to either the Station B or HB communities of other years. This larger analysis resulted in only minor changes in the relative positions of the Bay of Quinte SUs within stations. For example, the different zooplankton community structure identified in Figs Sa and 5b for 1992 at Stations HB and C, respectively, and for 2000 at Station B (Fig. Sa) were still evident after cluster analysis of all SUs together (Fig. 6). The larger analysis, though, has provided useful insights into the magnitude of these differences in the context ofthe other locations. Not only was the zooplankton community at Station B in 2000 (B-OO) very different from the other years at Station B (Fig. Sa), but it is now revealed that the B-OO zooplankton community (arrow, Fig. 6) was more similar to those at Station C than to any of those at Stations B or HB during any other year! The 1992 communities at Stations B and HB were more similar to each other than either was to any other Bay of Quinte SU (Fig. 6, group c). Among the reference lakes, Lake Simcoe and Sturgeon Lake (Fig. 6, group a) zooplankton

24 communities were very similar, with SUs of the same year being more similar than the same stations during different years. The opposite was true of the third reference location, Penetang Bay (Fig. 6, group b), for which inter-station differences were greater than the differences between consecutive years at each of the two stations. Zooplankton communities ofPenetang Bay as a· whole were more similar to the Bay of Quinte (especially the upper and middle bay in 1992) than to the other reference locations. Because the reference lake data relate best to the upper Bay of Quinte, where water depth and other limnological variables are comparable, further assessments (below) of the relationships between the Bay of Quinte and the reference locations included only Station B data from the Bay of Quinte. More variability was evident among the zooplankton communities of the reference lakes than at Station B (Fig. 7). The restricted analyses (Station B alone with the reference lake data) continued to demonstrate that the 1992 and 2000 zooplankton communities at Station B were very different from those found in other years. It is important to note also that the 1975 and 1976 communities (the most eutrophic years studied by Project Quinte) were the least like the reference lakes and generally, the 1990s communities were more like those of the reference lakes than the . 1980s communities in the upper bay (Fig. 7b). ANOSIM analyses were used to answer the question: Are the communities at Station B (both the pre-Dreissena and posillreissena commuuities, separately) significantly different from those at the reference locations? To keep the level of statistical power in these analyses identical, the pre-Dreissena time period used was the 6-year period 1989-1994, rather than the entire 1975- 1994 period; the.postDreissena data were from 1995-2000. Both the pre- and the posillreissena Station B zooplankton communities were significantly different from that representing the reference lakes. The ANOSIM R-statistic was 0.461 (P = 0.001) for the reference lake-pre­

Dreissena comparison, and 0.362 (P = 0.005) for the reference lake-post Dreissena comparison. SIMPER analyses identified which taxa contributed most to the differences in community structure between the post Dreissena Station B SUs and the reference lake SUs. The main taxa responsible for the difference in community structure between post Dreissena Bay of Quinte Station B (1995-2000) and the reference lakes included Eubosmina coregoni, Daphnia retrocurva, Chydorus sphaericus and Daphnia galeata mendotae, all with lower densities in the

25 reference lakes, and Bosmina longirostris, total calanoid copepodids, Daphnia pulicaria, littoral cladocerans, Leptodiaptomus minutus and Diacyclops thomasi, all with higher densities in the reference lakes than at Station B (Table 6). These ten taxa contributed more than 50 % of difference in community structure between the post Dreissena Station B and the reference lake zooplankton communities.

Zooplankton Community Function

Methods

The functional status of the zooplankton community was assessed by examining changes in total biomass (including veliger larvae), cladoceran biomass, the ratio oflarge to small Daphnia biomass, the mean length of the macrozooplankton (veliger larvae not included), and the ratio of predatory to herbivorous zooplankton biomass. These indicators were all calculated using the 01- May to 06-0ct seasonally-weighted mean abundances described above (p.ll). Abundances were converted to biomass using a set of assigned weights. Zooplankton length was not measured when the BoQ samples were originally enumerated because the cost was prohibitive: mean weights, determined by N.H.F. Watson and B. Wilson for Great Lakes' species were applied to the abundance data as per Cooley et al. (1986). Recently, collated samples were constructed for the June to September period for Belleville, Hay Bay and Conway for all years where original samples still existed, and reanalyzed for species lengths using a digitizing system. Therefore, all mean length estimates represent an average for the June-September period. It is generally thOUght that in open-water ecosystems that have a good balance of piscivorous to planktivorous fish, zooplankton mean length will be approximately 0.8 mm, when sampled with a 153-fUll mesh net, or 0.57 mm when sampled with a 64-Jlm mesh net (Mills et al. 1987, Johannsson et al. 1999). Ifa system is a nursery area for young-of the-year (yoy) fish, then the mean length of zooplankton in the summer may be lower than these values even if the fish community is balanced (Mills et al. 1987). Larger zooplankton species, such as Daphnia galeata mendota and D. pulicaria are selectively consumed by planktivorous fish, thus the ratio of large to small Daphnia (all other Daphnia species found in the BoQ) should increase as planktivory

26 decreases. Zooplankton total biomass should also be higher when the fish community is balanced than when it is dominated by planktivores. Without predatory control or with reduced predatory control, planktivores are likely limited by their food supply and consequently will depress their prey populations. On the other hand, decreases in phosphorus loadings to the bay have decreased

.~ phytoplankton biomass and reduced the food supply of zooplankton (Nicholls et al. 1986). The direction of changes in zooplankton biomass in the Bay of Quinte will depend on whether the community was limited more by predation of lack of suitable food The ratio of predatory to herbivorous zooplankton biomass is an indicator of the proportion of energy that passes to fish through the grazer versus the microbial food chain. The ratio was calculated using two different sets of assumptions. In the first, the 'maximum predatory ratio', all cyclopoid copepodids and adults were considered to be caruivorous. However, in reality, cyclopoids are omnivores (Balcer et al. 1984). In the second calculation ofthe ratio, the 'realistic predatory ratio', cyclopoid copepodids and adults were assumed to consume 50% animal and 50% plant biomass. The other predatory species present in the BoQ were Leptodora kindtii, Polyphemus pediculus, Cereopagis pengoi, Bythotrephes longimanus (also called eederostroemi), Episehura laeustris and Limnoealanus maerurus. Trends in the above indices across years were analyzed using the Mann Kendall Sigu Test, described in the previous section (p.l4). Trends were examined (a) across the entire time period- 1975 to 2000, (b) through the period prior to the Pinatubo volcanic eruption - 1975 to 1991, and (c) across the six years before and after the invasion by dreissenids - 1989 to 2000. The period 1976 to 1991 was included instead of the 1975 to 1994 period because the very cold conditions caused by the volcanic eruption were associated with a marked decline in zooplankton biomass and a slow recovery over the next couple of years leading up to the dreissenid invasion.

Results

Belleville In the upper bay, many significant changes occurred during the 1975-1991 period which did not continue through the zebra mussel invasion or were reversed. Although the Sigu Test did

27 not pick up a significant trend in total biomass through any of the periods (Table 7), total zooplankton biomass obviously doubled between 1981 and 1982 (Fig. 8). It remained high until the Pinatubo erruption in 1992. Recovery after 1992 was slow and arrested with the invasion of the bay by dreissenids. A Oneway Analysis of Variance indicated that the biomass in the 1982-

.~ 1991 period was significantly higher than the biomass either before or after that period (F = 16.2, 3 3 3 p <0.001): 0.41 g/m compared with 0.24 g/m and 0.26 g/m • Daphnia biomass also increased significantly from 1975 to 1991: perhaps thls trend was detectable because the increase in Daphnia biomass was more gradual. An increase in the biomass of large/small Daphnia also occurred and peaked in 1988 and 1995 at 7.68 and 9.68 respectively. In concert with these trends, zooplankton and cladoceran mean lengths increased, reaching a maximum of 0.48 mm and 0.59 mm respectively in 1988, stabilizing about 0.43 mm and 0.48 mm until 1999. Total biomass and Daphnia biomass were lower in the reference lakes. Total biomass ranged from 0.11 g/m3 to 0.36 g/m3 in Lake Simcoe and Sturgeon Lake to 0.07 to 0.15 g/m3 in Penetang Bay. Differences in - total Daphnia biomass were more pronounced amongst the reference sites: 0.04 g/m3 to 0.17 g/m3 in Lake Simcoe and Sturgeon Lake, but only 0.003 g/m3 in Penetang Bay. The role oftemperature and fish community structure in the reference lakes should be studied further before deciding on a desired biomass for the upper bay. Predatorratios showed no consistent trend between 1975 and 1991 (average of realistic predatory ratio = 0.10), although the percentage of cladocerans decreased slighly (but significantly), and the percentage of cyclopoids and calanoids increased slightly (Table 7, Fig. 9). Predatory ratios at the reference lakes Sturgeon and Simcoe were similar to that in the upper bay, 0.09 and 0.11 respectively, while that at Penetang was higher than any value observed in the upper bay, 0.19. This high value, together with the very low total biomass and biomass of Daphnia at Penetang Bay compared with the other reference lakes, suggests that the fish community in Penetang Bay was planktivore-dominated. The only change in zooplankton community indices coincident with the arrival of dreissenids, was a decline in the predatory ratios as the biomass of herbivores did not decline as much as that of predatory cyclopoids (50% of cyclopoid adult and copepodid biomass) (Table 7, Fig. 8, 9). Several other significant trends were observed during the 1989-2000 period, but none

28 strictly paralleled the dreissenid invasion. Some responses may have been confounded by the response to the exceptionally cold summer of 1992. The percentage of cladocerans increased and that of cyclopoids decreased in 1992 to levels observed prior to 1983 and did not recover (Fig 10). The ratio oflargelsmall Daphnia biomass decreased from 1988 until 1991. Daphnia biomass did

.~ not decline during the 1989-1999 period although total zooplankton biomass was lower from 1992 until 2000 than in the 1981-1991 period. 2000 appeared to be as unusual a year as 1992, in that strong declines were observed in total zoopl'ankton biomass, Daphnia biomass, and zooplankton and c1adoceran mean length (Fig. 8).

Hay Bay Total zooplankton biomass and Daphnia biomass increased significantly between 1975 and 1991 (Table 7). Like the pattern at Belleville, changes during the 1975-1982 period were slight: biomass increased sharply between 1982 and 1983 and fluctuated at this higher level until 1991. Total zooplankton biomass in the 1975-1982, 1983-1991, and 1993-2000 periods averaged 3 3 3 (mean ± s.e.) 0.23 ± 0.02 glm , 0.50 ± 0.04 glm , and 0.32 ± 0.02 glm respectively (Oneway

Analysis of variance, F = 18.09, P <0.001). While biomass increased and decreased in a step-like fashion, zooplankton and cladoceran mean length increased gradually through time reaching peak values of 0.46 mm and 0.52 in 1996 and 1997 respectively (Fig. 8). Lengths declined in 199912000 to 0.41 and 0.43 mm for total zooplankton and cladocerans respectively. The ratio of large/small Daphnia biomass followed the general pattern of changes in length: significant increasing trends were observed both in the 1975-1991 and 1975-2000 periods (Fig. 8, Table 7). The maximum ratio was observed in 1996: 4.98. The predatory ratios declined through out the period of study (Fig. 8). Significant trends were noted in the 'realistic predatory ratio' in each of the three time periods (Table 7). Variability was higher in the 'maximum predatory ratio': the trend was only significant across the entire time period. No indices changed significantly through the pre- post-dreissenid period (1989-2000) with the exception of the 'realistic predatory ratio' which was already declining. However, again like the situation in Belleville, total biomass never returned to levels observed prior to the Pinatubo eruption and the biomass of herbivores did not decline as much as that of predatory cyclopoids

29 after the arrival of dreissenids (Fig. 9).

Conway

The changes at Conway generally mirrored the patterns at Belleville and Hay Bay. Total zooplankton biomass increased sharply between 1981 and 1982 by the same proportion as at Belleville (170%) from an average of 0.09 ± 0.03 glmJ in the 1975-1981 period to 0.16 ± 0.04 glmJ in the 1982-1991 period (Fig. 8). After· the Pinatubo eruption which was credited with the cold spring of 1992, biomass started to climb again but only reached high values in one year (1996): it averaged 0.10 ± 0.04 glm) between 1993 and 2000. Biomass differed significantly amongst these three periods (Oneway Analysis of V ariance, F = 8.99, P = 0.002). Similar patterns were observed in Daphnia biomass (Fig. 8), and Daphnia contributed a gradually increasing proportion of zooplankton community biomass through out the period of study. Although there was a significant increase in the ratio oflarge/small Daphnia biomass over the 1975-2000 period, it was not discernible in either of the two sub-periods (Table 7). Higher ratios were observed as of 1992 with the maximum in 1996 (1.29) (Fig. 8). This value is still much lower than the ratios observed at Hay Bay and Belleville where values were> I in II years and reached peaks of 4.98 and 9.68 respectively. Zooplankton and cladoceran mean size increased over the period of study, but never reached as large as the values observed at Hay Bay and Belleville - mean lengths were generally near or below 400 Ilm. The predatory ratios decreased continuously through out the 1975-2000 period (Table 7, Fig. 8). A noticeable drop occurred between 1995 and 1996. Significant increases in the percentages ofcladocerans and calanoids were observed between 1975-1991 and 1989-2000 respectively, while cyclopoids declined slowly between 1975-1991. The lowest cyclopoid percentages occurred in 1996,1998-2000 (Fig. 10). At Conway, the only indices that definitely changed at the time of the dreissenid invasion of the BoQ, were the percentage of calanoids, which increased, and the predatory ratio, which decreased. The low percentage of cyclopoids in the late 1990s also fit the time frame, but not as cleanly (Fig. 10), and again the biomass of herbivores did not decline as much as that of predatory cyclopoids after the arrival of dreissenids (Fig. 9).

30 Discussion The distribution of zooplankton species and total zooplankton biomass in the Bay of Quinte indicate a spatial gradient in eutrophy consistent with other aspects of the Bay of Quinte linmology (Cooley et aI. 1986, Millard and Johnson 1986, Robinson 1986, Nicholls et al. 2002). Virtual lack of calanoids together with high densities and biorr;a~~ of cladocerans, particularly Bosmina longirostris, Eubosmina coregoni, and Chydorus sphaericus in the upper Bay are characteristic of eutrophic conditions. Moderate densities and biomass of cladocerans, the presence of Polyphemus pediculus and representation by cold, oligotrophic, stenotherms, such as Daphnia longiremis, Limnocalanus macrurus, and Leptodiaptomus sicilis in the lower bay are consistent with meso-oligotrophic conditions (Sprules 1977, Garmon and Sternberger 1978, Sternberger and Lazorchak 1994, Lougheed and Chow-Fraser 1998). The response ofthese zooplantkon communities to decreases in phosphorus loading to the bay, climatic events, and evolving fish community structure were assessed over the 1975-2000 period by investigating changes in zooplankton community structure, using multivariate analyses, and indices of community function, using trend analysis and Oneway Analysis of V ariance. Multivariate analyses of species composition, as portrayed in Fig. 5, illustrated how zooplankton community composition shifted firstly with the decline in phosphorus (1979-1981/2), secondly with the change in the fish community (1982/3-1991), thirdly with the climatic event (cold spring in 1992) caused by the eruption of Mount Pinatubo (effects observed only in 1992 (C) or later, 1992-1994 (B) ), and fourthly with the invasion of dreisenids (1995-2000). At each of these junctures, the zooplankton community composition changed position in 'community' space. The climatic event in 1992 set off high year-to-year variability in community structure at Belleville which continued after the arrival of dreissenids. At Hay Bay and Conway, community structure was displaced in 1992 and returned to the area of previous community positions by 1993 (HB) or 1994 (C). With the arrival of dreissenids, high inter-armual variability occurred at Conway, although not at Hay Bay. The ability to and rate with which a community returns to its initial state after a disturbance is a measure of the resilience of a community. These patterns in inter-armual variability, suggest that the community at Belleville was the least resilient ofthe three and that the impacts of dreissenids on the zooplankton community may not yet have stabilized or are

31 inherently more variable. Gradually, the species composition in the upper bay became more similar to that in the reference lakes during the 1975-1990 period, although never reaching similar composition. The recovery since 1975 has not been especially dramatic, given the marked decline in point-source

.~ phosphorus loading that has occurred (Project Quinte 2001). The depressed calanoid biomass in the upper bay compared with the reference sites, together with the high densities of cyclopoids and small cladocerans may suggest a level of ecosystem degradation more significant than that inferred by its eutrophic status alone. Sternberger and Lazorchak (1994) found that domination by small cladocerans, copepod nauplii and copepodids was typical of most highly disturbed systems among a group of 19 New England lakes. Keller and Yan (1998) identify four possible zooplankton community types that result from the recovery process: (i) a community limited by dispersal, (ii) a community limited by biological resistance, (iii) a community very like the original (pre-stress) community, and (iv) a normal, but different, community. While their assessment drew heavily on their experience with the recover of acidic lakes, they suggest that certain principles of recovery based on the . acidification/neutralization model likely also apply to other perturbed systems. In the Bay of Quinte context, which of the four scenarios described by Keller and Yan (1998) could conceivably develop? i) Opportunities for re-colonization by species inhabiting upstream, less-stressed aquatic systems, are certainly great because ofthe Bay of Quinte's hydrologicaUphysiographical setting as the terminal basin of the Kawartha Lakes. Therefore, community composition and function are unlikely to be limited by dispersal. ii) Biological resistence may be caused by: 1) an imbalanced fish community consisting of excessive biomass of zooplanktivores relative to piscivores, 2) scarcity of rooted aquatic macrophytes (refuges for daphnids, e.g. Christoffersen (1998)),3) an imbalance in, and/or a depletion offood resources (small-celled phytoplankton species, other small organisms such as rotifers) resulting from the establishment of Dreissena, and 4) establishment of other exotic,

32 invading species (e.g. Bythotrephes, Cercopagis, Neogobius) with potential to impact directly (by predation) on important zooplankton species. Bythotrephes and Cercopgis are predatory cladocerans, Neogobius, the round goby, is a benthivorous fish. Considering each of these each in turn: 1) From the zooplankton perspective, the fish community in the Bay of Quinte improved considerably in the early 1980s with the increase in the walleye population (piscivores) and decline in white perch (omnivore) and later alewife (mainly planktivore) (Hurley and Christie 1977, Hurley 1986). In this new community, white perch now grew rapidly and became piscivorous. Thus the balance between piscivores and planktivores shifted towards piscivores. The zooplankton community responded with increases in biomass and productivity (Moore 1995), individual mean size (zooplankton mean length) and changes in species composition. This increase occurred in spite of a 30%-50% decrease in edible aglae, defined as the sum of cryptophytes, chrysophytes, and half of the chlorophytes, between 1975-1976 and 1979-1983 (derived from Table 2 of Nicholls et al. 1986). The decrease in algal biomass was associated with the reduction in phosphorus loadings to the bay. The F-index of Nicholls also did not improve between 1975 and 1994 (Nicholls 200Ic). This index considers the relative biomass of bloom-forming blue-green algae, which interfer with cladoceran feeding, to the biomass of edible algae, defined as the sum of cryptophytes and chrysophytes in this index. The lack of improvement in the food supply indicates that the improvements in the zooplankton community during the 1980s were due to changes in the fish coriununity. The arrival of dreissenids did not immediately change the balance in the fish community. However, the high filtering capacity of dreissenids increased light penetration which assisted in the re-establishment of the macrophyte beds. These changes in habitat are thought to be responsible for the relocation of walleye, and resurgence of yellow perch, bass and pan fish (Stewart et al. 2000). The decline in zooplankton mean length in 2000 may reflect a shift away from a more piscivore-dominated community particularly in the upper and middle bay. However, 2000 was an unusual year for zooplankton and any trends in zooplankton biomass and mean length (i.e. impact of the balance ofpiscivores and planktivores) need to await future data.

33 2) Scarcity of macrophytes is not likely to be a problem. Density of the macrophyte beds (percent cover) started to increase in the early 1990s with the improvement in light conditions, the rate of increase augmenting as of 1994 (Seifried 2001). In 2000, the

.~ percent cover within the macrophyte beds of the entire bay reached 73%. The areal extent of macrophyte beds has generally not changed, although some data suggest that macrophytes were expanding into deeper water by 2000. The fmal impact of this habitat change on the zooplankton community in open waters may need to await the full colonization of the macrophyte beds by littoral zooplankton species, invertebrates and fish. Therefore, at the moment, past-loss of macrophytes may be a limitation, but in the long­ term, should not considered to be a major biological limitation, providing action is not taken to reduce these beds again.

3/4) The structure and quantity of food resources, on the other hand, have been influenced by dreissenid filtering activity (Nicholls 2001c) and are expected to remain a biological limitation for the zooplankton community. The phytoplankton species mix has changed with decreases in chlorophytes, some of which are eaten by cladocerans, dinoflagellates and certain diatom species and increases in the blue-green alga, Microcystis. Primary production has decreased through out the bay beyond that predicted by total phosphorus levels since the arrival of dreissenids (Millard and Burley 2001). Zooplankton production (and biomass) is controlled partially by the level of primary production (Makarewicz and Likens 1979). When dreissenids depressed primary production in Lake Erie (Millard et al. 1999), zooplankton production followed suite (Johannsson et al. 2000). The same phenomena appears to be happening in the Bay of Quinte where total zooplankton biomass remained lower after the Pinatubo event and the arrival of dreissenids although zooplankton mean length did not indicate any immediate change in the level of planktivory - the other important factor controlling zooplankton production and biomass.

Dreissenids are known to eat rotifers (Shevtsova et al. 1986 in MacIsaac et al. 1995,

34 MacIsaac et al. 1995) which form part of the microbial foodweb leading through cyclopoids to fish. This raises the question of whether rotifer abundance has decreased and if a decrease were in some way partly responsible for the greater declines in cyclopoids than cladocerans after the dreissenid invasion. Unfortunately, no data are

.~ available to address that question. However, more importantly, the proportionately greater decline in cyclopoids, which contribute to the significant declines in the predatory ratio, signals a shift in the relative importance of the grazing and microbial food webs when dreissenids dominate the system. The grazing food web is more direct and efficient at delivering energy to fish and is now relatively more important. The rnicrobialloop is based on recycled and imported carbon sources which support bacterial production and on autotrophic (picoplankton) production; however, the pathway is less efficient at delivering energy to fish through the plankton due to the increased number of trophic levels. On the other hand, it does capture external energy sources and recycle nutrients which increase the productivity of nearshore regions like the Bay of Quinte. Is the rnicrobialloop now more efficient because it passes through a larger invertebrate (Dreissena) to fish (albeit different fish) or are these functions now impaired in the Bay of Quinte due to suppression of rotifer biomass?

4) Bythotrephes longimanus which entered Lake Ontario in the mid-1980s is presently contolled by alewife predation. The impacts of Cercopagis pengoi and Neogobius melanostomus two new exotics which entered the Bay of Quinte in 1999, are not yet know. Neither is presently abundant in the upper or middle bay. Cercopagis pengoi is abundant in July and August in the lower bay (Benoit et al. 2002). Data, to this point, suggest that they may depress the abundance of cyclopoid and calanoid nauplii and copepodids as well as small cladocerans, such as Bosmina, when they are abundant (Benoit et al. 2002). A number of fish predators of Cercopagis have been identified in Europe: smelt, three­ spined stickleback, and herring amongst others (Ojaveer and Lumberg 1995; Rivier 1998; and Yankovskii 1970 cited in Grigorovich et al. 2000, Ojaveer et al. 2000). However, only alewife has been positively identified as a predator in North America.

35 Gobies consume macrobenthos, including dreissenids, as of age one (French ill and Jude 2001, Simonovic et al. 2001). Young-of-the-year fish likely start feeding on zooplankton before turning to a benthic diet. This species can reproduce several times during the summer; consequently, the impact of its young on the plankton would be continuous through the year. Given the abundance of food available for adults, and the potential for high reproductive rates, the impact on the zooplankton community might be significant if they became abundant. In turn, depressed zooplankton biomass could have ramifications through out the fish community ifthe young gobies were sufficiently abundant. iii) The reference lake approach indicated that the 'likely' pre-stress zooplankton community structure in the upper bay had not been attained with present decreases in phosphorus loadings or improvements in the fish community even before the arrival of dreissenids. The arrival of dreissenids caused environmental changes which mimicked expected further improvements in trophic status. The full impact of these changes on zooplankton composition may not yet have played out. However, dreissenids also exerted their own impact on the zooplankton community: direct competition of veliger larvae, dreissenids and cladocerans for reduced levels of primary production, decreases in food resources of cyclopoids, comsumption of rotifers and likely small nauplii (Shevtsova et al. 1986 in MacIsaac et a. 1995, McIsaac et al. 1995, Johannsson et al. 2000). Even if all zooplankton groups are reduced, it is likely the balance amongst groups will have been altered, as we noted with the greater reduction in cyclopoids than cladocerans after dreissenids arrived. The invasion of the bay by exotics, particularly herbivorous or carnivorous planktonic forms (veliger larvae, Cercopagis, Bythotrephes), mean that the zooplankton community can never return to the pre-stress condition of the past. iv) The arrival of exotic zooplankton from other continents may mean that the zooplankton community in the Bay of Quinte can never strictly return to a known normal community as it would now be composed of a mix of North American and non-North American species. The degree of displacement would likely depend on the relative importance of the new species in the

36 system and whether they changed the balance between other zooplankton species or diverted energy to other habitats (benthic, macrophyte). The reference lake approach employed here has been a very useful tool to examine the response of the zooplankton community in the upper bay to remediation actions, climatic events and the invasion of an exotic. The arrival of dreissenids did alter the structure of the zooplankton community and increased its variability. In some years it was more similar to the reference lakes (95, 98) while in others it was less similar (96, 97). Future work on this subject should endeavor to obtain zooplankton data from some other deep-water embayments of the Great Lakes (e.g. Twelve-Mile Bay of Georgian Bay and South Bay on Manitoulin Island) that could serve as analogues for a less-stressed lower Bay of Quinte community and thus as restoration targets for zooplankton community structure in the same way that the upstream Trent-Severn Waterway locations have served for the upper bay.

Conclusions Eutrophication, high levels of planktivory and possibly other related stresses apparently contributed to a perturbed crustacean zooplankton structure in the Bay of Quinte. Prior to major reductions in point-source phosphorus loading in 1977 and when the fish community was still dominated by planktivores, zooplankton community structure in the upper bay was most unlike those of reference (target) lakes. Since then, however, there have been changes that may indicate some recovery; these were manifested at the whole-communityOlevel by increases in total biomass, mean individual size, ratio oflarge/small Daphnia biomass, decreases in predatory ratio, and changes in community composition to a structure more similar to that represented in the reference lakes. Increased inter-armual variability in zooplankton community structure in the upper and lower bay was associated with the establishment of zebra mussels in the bay in 1995. In order to further the trend towards the target community composition, there will have to be reductions in upper Bay of Quinte densities of Eubosmina coregoni, Daphnia retrocurva, Chydorus sphaericus and Daphnia galeata mendotae and increases in Bosmina longirostris, Daphnia pulicaria, total calanoid copepodids, littoral cladocerans, Leptodiaptomus minutus and Diacyclops thomasi. These 10 species/taxon groups accounted for more than 50 % of the dissimilarity between the upper Bay of Quinte and reference lake zooplankton communities. The

37 zooplankton community is, therefore, still considered impaired. Decreases in the relative abundance of cyclopoids with the arrival of dreissenids, the marked decrease in zooplankton biomass and mean size in 2000 and the potential impacts of Cercopagis pengoi and Neogobius melanostoma are cause for concern with regards to the 'integrity' of the zooplantkon community. They will need to be evaluated with respect to a final expected 'normal' zooplankton community.

Acknowledgments Data from the reference lake locations were from the Ontario Ministry of the Environment. Drs Murray Johnson and Ken Minns and Mr. Scott Millard have acted as Program Leaders of Project Quinte over the years. Mr. James Moore was responsible for processing the zooplankton data until 1994. Field co-ordination has been provided by Mr. Charles Timins, Ms. Debra Myles and Ms. Michele Burley over the years. Many summer students have assisted with the sampling. The work of all these people is gratefully acknowledged.

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47 Table 1. Comparison of several morphometric and linmological variables of the upper and middle Bay of Quinte (Stations B and HB, respectively) with three other southern Ontario locations deemed suitable as "references" for their less impacted zooplankton communities: Sturgeon Lake (Kawartha Lakes, Trent Severn Waterway), Cook's Bay of Lake Simcoe, and Penetang Bay of Severn Sound (southern Georgian Bay). Reference lake data are for 1987-88, prior to the establishment of zebra mussels. Data for the Bay of Quinte are for the pre-phosphorus control period, 1972-1977.

Mean depth Flushing Rate Secchi disk Specific Total phosphorus Chlorophyll a (m) (yr'!) visibility (m) Conductance (,ugIL) (,ugIL) (,umhos/cm)

Upper Bay of Quinte 3.5a l1.7a 1.2b 230' 78b 28b Middle Bay of 5.2a 23.5 l.4b 250' 53b 22b Quinte (144)" Sturgeon Lake 3.5' 9.5" 2.7d 220d 28 d 9.0d

Cook's Bay 12.8g 0.35 g 3.1f 340h 20f 4.2f

Penetang Bay 4.7i 0.7i 2.1 ' 204' 26i 11.8'

Data sources: a Minus et al. (1986b) [value in parenthesis (144) is after correction for Lake Ontario backflows]; b Robinson (1986); 'Ontario Ministry ofthe Environment, unpublished data; d Hutchinson et al. (1994a); 'Hutchinson et al. (1994b); fNicholls (200la); g Nicholls (2001b); h Nicholls (1995); i Sherman and Brown (1995).

48 Table 2. List of crustacean zooplankton species occurring at each of the three Bay of Quinte sampling stations (B, HB and C) and the number of years each was recorded at least once during the May I - October 6 time period of each year during 1975,1976 and 1979-2000.

Number of Years B HB C Cladocerans Acroperus harpae I 0 I Alana affinis 2 0 1 Alana guttata 9 10 5 Alana quadrangularis 11 5 4 Alana rectangularis 2 0 0 Alana sp. 9 4 1 Bosmina longirostris 24 24 24 Bythotrephes longimanus 0 0 1 Camptocercus rectirostris 1 0 0 Cercopagis pengoi 2 1 2 Ceriodaphnia lacustris 24 24 24 Ceriodaphnia pulchella 2 2 2 Ceriodaphnia quadrangula 3 3 4 Ceriodaphnia sp. 4 1 3 Chydorus globosus 1 0 0 Chydorus sphaericus 24 24 24 Daphnia ambigua 2 6 2 Daphnia catawba 3 1 2 Daphnia galeata mendotae 24 24 24 Daphnia longiremis 2 8 9 Daphnia pulicaria 12 15 14 Daphnia retrocurva 24 24 24 Daphnia sp. 2 1 5 Diaphanosoma birgei 24 23 24 Diaphanosoma brachyurum 1 1 0 Eubosmina coregoni 24 24 24 Eubosmina longispina 0 0 1 Eurycercus lamellatus 11 9 2 Holopedium gibberum 7 22 24 Ilyocryptus spinifer 4 1 0 Latona setifera 1 2 1

49 Table 2, cont'd B HB C

Leptodora kindtii 21 17 21 Leydigia quadrangularis 1 5 1 Ophryoxus gracilis 1 1 ~O Pleuroxus denticulatus 2 0 0 Pleuroxus procurvus 3 0 0 Pleuroxus sp. 1 0 0 Polyphemus pediculus 1 1 9 Sida crystallina 5 5 4 Simocephalus settulatus 1 0 0 Simocephalus vetulus 0 0 1 Calanoid copepods Epischura lacustris 2 2 1 Eurytemora affinis 15 15 23 Leptodiaptomus ashlandi 1 1 3 Leptodiaptomus minutus 10 10 11 Leptodiaptomus sicilis 1 6 16 Leptodiaptomus siciloides 16 23 17 Limnocalanus macrurus 2 5 S Skistodiaptomus oregonensis 15 22 24 Skistodiaptomus reighardi 0 1 2 Cyclopoid copepods Cyclops scutifer 0 1 1 Cyclops varicans rubellus 1 0 0 Cyclops vernalis 24 24 23 Diacyclops thomasi 23 24 24 Ergasilis sp. S 4 3 Eucyclops agilis 15 9 5 Eucyclops speratus 4 2 0 Mesocyclops americana 2 3 0 Mesocyclops edax 24 24 24 Tropocyclops extensus 24 24 24

50 Table 3. Results of ANOSIM analyses comparing zooplankton community structures at Stations B, HB and C in the Bay of Quinte before and after phosphorus control and before and after establishment of zebra mussels (Dreissena). Comparisons were also made (part II) after

omitting 1992, which had anomalous zooplankton characteristics~ likely caused by record low

water temperatures. (1) = comparison of pre-P control (1975-76) with pre-Dreissena (1989- 1994); (2) = comparison ofpre-P control (1975-76) with post Dreissena (1995-2000), and (3)

= comparison of pre- and post Dreissena (1989-94 vs 1995-2000).

StationB StationHB Station C

PART! (1) (2) (3) (1) (2) (3) (1) (2) (3)

Sample statistic (Global R) 0.344 0.354 0.181 0.458 1.0 0.235 0.615 0.760 0.272

Iprobability 0.143 0.179 0.035 0.071 0.036 0.011 0.036 0.036 0.024

PART II (1) (2) (3) (1) (2) (3) (1) (2) (3)

Sample statistic (GlobaIR) 0.691 0.354 0.261 0.800 1.0 0.339 0.764 0.760 0.304

Iprobability 0.048 0.179 0.017 0.048 0.036 0.011 0.048 0.036 0.013

I Probabilities (determined by permutation - see Methods section) greater than 5 % (0.05) imply that the differences are not likely significant

51 Table 4. Mean densities of Bay of Quinte Station C zooplankton taxa in SU group I, the pre­ phosphorus control years (1975-76) and SU group II, the pre-Dreissena years (1989-94, but omitting 1992) arranged in order of their percentage (%) contributions to the average dissimilarity between the groups. Also listed are the values of .0,J SD(o,), where OJ is the average contribution of taxon i to the overall dissimilarity between the two groups. Where "%" and the ratio OJ -to-SD(o,) are both relatively high, taxon i is an important and consistent contributor to the inter-group dissimilarity (see Methods section).

3 Mean density (#/m ) Groups I and II

Taxon Group I Group II OJ /SD(o,) % (1975-76) (1989-94) cyclopoid nauplii 4373.4 14620.4 4.57 7.2

Daphnia galeata mendotae 30.5 853.3 2.12 6.9

Daphnia longiremis 60.9 0 1.45 5.2 littoral cladocerans 1099.0 3757.7 2.16 5.1

Limnoclaanus macrurus 13.3 0 16.85 4.9

Daphnia retrocurva 1456.8 4443.5 1.88 4.7

Bosmina longirostris 13766.2 23414.6 1.35 4.6 cyclopoid copepodids 9351.0 19033.1 2.59 4.6

Eubosmina coregoni 3225.6 8244.1 1.18 4.6 total calanoid nauplii 108.4 624.1 1.54 3.9

Leptodiaptomus sidloides 23.8 46.9 1.68 3.5

Leptodiaptomus minutus 31.9 6.2 1.36 3.2

Daphnia pulicaria 0.13 11.5 1.79 3.2

Holopedium gibberum 3.2 44.4 2.86 2.9

Chydorus sphaericus 2468.9 1949.6 1.48 2.9 benthic cladocera 2.1 2.2 3.81 2.7

52 Table 4 cont'd

3 Mean density (#/m ) Groups I and II

Taxon Group I Group II o,/SD(8) %

Polyphemus pediculus 0.2 6.8 1.46 2.6

Cyclops vernalis 109.0 56.6 0.74 2.6

Eurytemora affinis 49.8 17.5 0.93 2.5

Tropocyclops extensus 1098.5 926.5 1.08 2.4

Leptodora kindtii 40.7 17.2 0.92 2.3

Leptodiaptomus sicilis 10.9 3.2 1.15 2.2

Skistodiaptomus oregonensis 7.4 46.2 2.27 2.2

Daphnia ambigua 0.8 0 3.25 2.1

Mesocyclops edax 125.7 206.4 1.49 1.9

Diaphanosoma birgei 124.0 191.8 1.31 1.8 total calanoid copepodids 872.7 874.5 1.38 1.7

Diacyclops thomasi 1367.1 1258.6 1.34 1.5

Daphnia sp. 0.4 0 0.95 1.2 benthic copepods 0.3 0 0.95 1.1

Leptodiaptomus ashlandi 0.2 0 0.95 1.0

Daphnia catawba 0.2 0 0.95 1.0

53 Table 5. Mean densities of Bay of Quinte Station C zooplankton taxa in SU group II, the pre­ Dreissena years (1989-94, but omitting 1992), and SU group III, the post Dreissena years (1995-2000) arranged in order of their percentage ( %) contributions to the average dissimilarity between the groups. Also listed are the values of .Ii ;! SD(Ii;), where /); is the average contribution of taxon i to the overall dissimilarity between the two groups. Where "%" and the ratio /); -to-SD(Ii;) are both relatively high, taxon i is an important and consistent contributor to the inter-group dissimilarity (see Methods section).

3 Mean density (#/m ) Groups II and III

Taxon Group II Group III /); /SD(Ii;) % (1975-76) (1989-94)

Bosmina longirostris 23414.6 8191.1 1.41 8.1 cyc1opoid copepodids 19033.1 7684.2 1.97 7.3

Eubosmina coregoni 8244.1 2679.6 1.40 6.7

Chydorus sphaericus 1949.6 2529.8 1.28 5.8

Tropocyclops extensus 926.5 230.8 1.68 5.2

Leptodiaptomus siciloides 46.9 20.4 1.20 4.6 total calanoid nauplii 624.1 1532.4 1.28 4.3

Daphnia pulicaria 11.5 0.7 1.58 4.0 littoral c1adocerans 3757.7 4117.3 1.21 4.0

Daphnia retrocurva 4443.5 3838.1 1.23 3.6 Diacyclops thomasi 1258.6 1193.9 1.21 3.4

Daphnia galeata mendotae 853.3 823.9 1.29 3.3

Daphnia sp. 0 8.8 1.28 3.3

Polyphemus pediculus 6.8 7.4 1.19 3.2

Leptodiaptomus minutus 6.2 3.9 1.20 3.2

Cyclops vernalis 56.6 34.2 1.21 3.0

54 Table 5 cont'd

3 Mean density (#/m ) Groups II and ill

Taxon Group II Group ill OJ /SD(Ii,) % (1975-76) (1989-94)

Leptodora kindtii 17.2 13.1 1.10 3.0 cyclopoid nauplii 14620.4 11861.3 1.25 2.8

Eurytemora affinis 17.5 46.0 0.97 2.7

Leptodiaptomus sicilis 3.2 1.0 1.14 2.5

Mesocyclops edax 206.4 165.7 1.43 2.4

Holopedium gibberum 44.4 116.5 1.25 2.2 total calanoid copepodids 874.5 730.7 1.38 2.1 benthic cladocera 2.2 3.6 0.66 1.7

Skistodiaptomus oregonensis 46.2 89.9 1.20 1.7

Skistodiaptomus reighardi 0 2.0 0.69 1.5

Diaphanosoma birgei 191.8 200.6 1.18 1.4

Limnoclaanus macrurus 0 1.0 0.69 1.3

Daphnia catawba 0 3.3 0.44 1

Daphnia longiremis 0 2.4 0.44 0.9

55 Table 6. Mean densities of zooplankton taxa in the reference lakes and at Bay of Quinte Station B, 1995-2000 (post Dreissena) arranged in order of their percentage (%) contributions to the average dissimilarity between the two groups. Also listed are the values of 0, / SD(8,), where 0, is the average contribution of taxon i to the~ overall dissimilarity between the two groups. Where "%" and the ratio 0, -to-SD(8,) are both relatively high, taxon i is an important and consistent contributor to the inter-group dissimilarity (see Methods section).

3 Mean density (#/m ) Ref. Lakes and Stu B (1995-200)

Taxon Ref. Lakes B (1995-2000) o,/SD(8,) %

Eubosmina coregoni 6065.3 25315.7 1.89 5.9

Bosmina longirostris 55964.4 16989.9 1.26 5.7 total calanoid copepodids 7513.3 437.5 1.73 5.7 Daphnia pulicaria 2662.1 20.4 1.28 5.6 Daphnia retrocurva 1322.3 9917.3 1.46 5.4 Chydorus sphaericus 6169.7 10065.6 1.68 5.4 littoral c1adocerans 5360.5 3065.2 1.70 4.7

Leptodiaptomus minutus 426.8 0 1.65 4.5

Daphnia galeata mendotae 2582.8 6338.9 1.22 4.4 Diacyclops thomasi 1461.7 74.2 1.84 4.3

Skistodiaptomus oregonensis 1675.5 35.1 1.48 4.1 cyclopoid nauplii 46982.5 21825.6 1.39 3.7

Holopedium gibberum 847.8 23.6 1.17 3.5 cyclopoid copepodids 24261.7 9752.6 1.59 3.5 total calanoid nauplii 5064.8 1896.5 1.30 3.3 Cyclops vernalis 68.2 509.2 1.49 3.3 benthic cladocera 7.7 44.3 1.53 2.4 Diaphanosoma birgei 1506.0 2077.8 1.56 2.3

56 Table 6 cont'd

3 Mean density (#/m ) Ref. Lakes and Stn B (1995-200)

Taxon Ref. Lakes B (1995"2000) I);/SD(,S;) %

Leptodora kindtii 27.6 53.5 1.72 2.2

Mesocyclops edax 1399.6 1304.5 1.34 2.2

Tropocyclops ex;tensus 1276.4 739.2 1.53 2.1

Leptodiaptomus siciloides 0 69.5 0.98; 2.1 benthic copepods 11.6 26.2 1.27 1.9

Daphnia longiremis 63.3 0 0.91 1.9

Leptodiaptomus sicilis 43.6 0 0.69 1.5

Epischura lacustris 14.3 0 0.79 1.2

Polyphemus pediculus 3.3 16.2 0.67 1.1

Daphnia sp. 0 11.5 0.67 1.0

Eurytemora affinis 0 8.9 0.69 0.9

Daphnia dubia 17.0 0 0.55 0.9

Leptodiaptomus ashlandi 7.6 1.9 0.63 0.9

Daphnia parvula 14.0 0 0.56 0.8

Daphnia catawba 0 3.6 0.70 0.8

Cyclops scutifer 1.7 0 0.55 0.5

Daphnia ambigua 4.6 0 0.30 0.3 littoral copepods 2.4 0 0.30 0.2

57 Table 7. Probability of a significant trend across years, as determined by a Mann Kendal Sign Test, in a range of zooplankton community variables at three sites in the Bay of Quinte: B (Belleville - upper bay), HB (Hay Bay - middle bay) and C (Conway - lower bay). Four time periods were examined: the whole data series (1975-2000), the period of decreasing total phosphorus and changed fish community before the eruption of Pinatubo (TPlFish 1975-1991), the pre-dreissenid period (TPlFish 1975- 1994) and the period bracketing the strong colonization by zebra mussels in 1995 (1989-2000). Bolded values indicate a downward trend, while italicized values indicate an upward trend.

Date Range Entire Time (1975-2000) TPlFish (1975-1991) TPlFish (1975-1994) Pre-Post ZM (1989-2000) Station B HB C B HB C B HB C B HB C Zoo ML (no veligers) 0.0002 0.0432 0.0041 0.0334 0.0002 0.0495 0.0128 Cladoceran ML 0.0001 0.0484 0.0118 0.0009 0.0114 0.0001 0.0015 0.0432 %Cladocera 0.0057 0.0008 0.0139 0.0056 0.0266 0.0185 %Copopepods 0.0057 0.0008 0.0139 0.0009 0.0266 0.0185 %Cyc1opoida 0.0043 0.0008 0.0239 0.0021 0.0316 %Calanoida 0.0345 0.0221· 0.0370 Total Biomass 0.0015 0.0300 Daphnia Biomass 0.0001 0.0088 0.0004 0.0038 0.0003 0.0407 %Daphnia Biomass 0.0483 0.0002 0.0000 0.0211 0.0244 0.0025 0.0009 0.0271 LIS Daphnia Biomassb 0.0023 0.0000 0.0004 0.0005 0.0007 0.0004 0.0001 0.0048 0.0196 Pred (M)lTotal Biomass' 0.0410 0.0000 0.0001 0.0452 0.0019 0.0086 0.0329 0.0400 0.0234 Pred (R)lTotal Biomassd 0.0337 0.0000 0.0000 0.0481 0.0003 0.0039 0.0080 0.0386. 0.0212 0.0196 ': Zoo ML - zooplankton mean length (crustacean zooplankton and veliger larvae) b: LIS = ratio oflarge Daphnia biomass (i.e. D. g. mendotae, D. pulicaria) to small Daphnia Biomass (all other Daphnia) ': Pred (M)lTotal = ratio of predatory zooplankton biomass (Leptodora, Polyphemus, Cercopagis, Limnocalanus, Epishcura, all cyclopoid adults and copepodids) to total zooplankton biomass (no veliger larvae) d: Pred (R)/Total = ratio of predatory zooplankton biomass (as above but the copepods were assumed to be ouly 50% carnivorous) to total zooplankton biomass (no veliger larvae).

58 I-AA"'" N

44°05' N

:to 43'S5'N s Lake Ontario

77'35'W 77'1S'W 76'55' W

Figure 1. Map of showing the locations of three main zooplankton sampling stations in the Bay of Quinte (B, HB and C).

59 301 Station B 30 I Station HB

25 25

-(20 -(20 en en '0 '0 .8 15 .8 15 E E :::I :i 10 Z 10 ~ ~ 5 I ~ I- 5

T 1979'1S-81' id85' 1987'1d89"'Hi91! 1!193'1995!'ui97' Hf99' 1979' 1981'1983'1985'19'87' ni89' 1991" 1993 1995' 1997' 1999 o 1~:' o 19~)76 1980 1982 -1964 1986 1968 1990 1992 1~941996 1998 2000 19~)76 1980 1982 1964 1986 1988 1990 1992 1994 1996 1998 2000

301 Station C f.J cydopoid copepods o calanoid copepods • cladocerans II 25 120 '0 Figure 2. Total uumbers of species in each of f5 the three major zooplankton groups at the three Bay of Quinte sampling stations (B, HB Z 10 ~ and C) occurring in each May 1- October 6 I- 5 period of each of the years 1975, 1976, 1979- 2000. 0 1975 1979'1981' 19"83' Hi8S'1987' 19"89' 19'91'1993" 19"95'1997'1S-99 1976 1980 1982 1964 1986 1988 1990 1992 1994 1996 1998 2000

60 INCREASE DECREASE.

1975-2000 1975-1994 '')71: 11111 l';f I;,-l9<>4 B IHB C B IHB C B [fm C B IJm ,r cladocera

H"V'~ • • • • Bosmina longirostris • • I. C"Y"V< "" -1' ,.~"" • • Ie, I.' Daphnia galeata mendotae I. I. • i~ r: • • • I . . "" Daphnia retrocurva •• • • • I. A total r: spp. • • coregoni • • • I.• I. Holopedium 6' • • . • • • • Ie k_ Diaphanosoma birgei • •

'n' • total r~l~n,,;rl nauplii • total calanoid -. . 1. • • • • I.I. total adult • • T minutus • • • .,'.' Skistodiaptomus oregonensis • • • • • ,-, sici/is • • • • • I. Leptodiaptomus C macmrus • • • • Eurytemora affinis I.• copepods •• r: -J -1' • • • • Cyclops vernalis • • • ~Y~>V¥"' edax • • • • Tropocyclops extensus • • • • • total adult CYC1OPl"uo • • .' I. cyclonoid • • • "v,,1 in. • • • • ~I.

Figure 3. Summary of increasing and decreasing trends in crustacean zooplankton taxa at Bay of Quinte Stations, B, HB and C during 1975-2000, and the pre-zebra mussel time period, 1975-1994. Those marked (e) indicate at least the 95 % level of significance (non-parametric sign tests).

61 b c

1g

Stn C "E 25 Daphnia puticaria lpo ~t5 o 5i 10 c 5

j 2.5 -r--=___ ------, k 2 0 1. j 6 total ~20 calanoid g1.5 g g 15 ~ 4 nauplil o ~1.0 o ~10 &iO.5 c ~ 5

Figure 4. Dreissena veliger larval densities and densities of those zooplankton species and taxon groups showing statistically significant differences (Mann-Whitney U-tests) between 6-year pre- and post Dreissena time periods (1989-1994 vs 1995-2000).

62 a 70 Stn B b 70 Stn HB C SO StnC ~ ~ ~ fao fso f (/) (/) ,l- 190 ,J- -L~ f 90 90 - ~ :I ~rrl

1 tIII 11001 I I I I I I I I I I I I I I I I I I I I I I I I 100 100~~~~~;;~~~;;~;~~~;;~~;;; xxxxxxxxxxxxxxxxxxxxxxxx g~~g~gg~gg~ggg~~ggg~g~~~ o~mo~~m~f~~m~~QfwN_O~m~N~~~~~~~~~~~~~~~~~~~~~~~~ o~~~~~~f~=~~~o~8~~m~~~~:!l iSlrass = 0.16 ~treas - u. , .. ISIrass = 0.13 '93 [~8""" 65 7"S'; '92 /'~~~;~.~~j '91 '92 '90 ; ..... '~5 ('P.O' ... :~~) '90 '89,88 '88 '1iWl j'99 i.~3···...... !'96 '971 ...... '94 '86 '87 -I .. ··· -I .... :. ~' '92 '83 '85 'ap 1'82 .(4 '~i7 '8~6";~ij" ...... ' '93 '94 8 '82 '85 '84 79

Axis I

Figure 5. Clustering and ordination of zooplankton species abundance data (24 years of May-October weighted means) for each of the three Bay of Quinte stations, B (a), HB (h) and C (c). The year is indicated by the double digit; for example, Station HB in 1979 is coded as HB-79. The dashed lines in each ofthe three ordinations enclose the pre-phosphorus control years (1975 and 1976) and the post zebra mussel years (1995-2000),

63 .. ~ 01 .9 81 Q'I a:s I 811~8 .. U I J ~ ~ I ~t ~ .. =01 ..Q II:> ...Q U ..c g~ or 0'" .iOI 0 01 0 ~ ..:l 6 Q 1B-79 ., = r--1 .. ..~ ~ <:I .. 8-88 .• 8-89 = s B-90 rI.l '--- ~ '-- ~ .•= ~ rLr B-83 ~ Q~ ... I R:g~ Q) '" rI.l B-96 =Q I B-76 ...... Q) B~1 .iOI =rI.l HB-75 '-' HB-76 =01 ., HB-79 1:1. -Q Q= Q N aH~ N ~ B-95 ...... ~ 1t1l3 cD' Q -Q "0 ...... = =f:: ~~ ..'"= ~ ~~ ...., f:: ' H8-89 .. ~ HB-90 oS '-l H8-91 01= 8-98 .•= B-97 ., U --- -Lr 8-91 .. ~ B-99 .• - =01 '-- - HB-96 = - HB-95 ..01 ~ HB-97 = HB-98 - HB-88 .•·s., =~ HB-99 ~ =., 01 ~ .. C-96 ,e Q= = C-75 01 .•... ~ 01 C-76 -.. ... =01 - .. rI.l ..... - §j -= ...... = - rl-r g:sg "';., .9 ~ C-79 .-= 0'= .•= ~ ...... , ~ ~ Cl _---4 Cl -= Q ., .... ~ - 8:3l 01 EI 01 01 = ... =~ ... ~ ~ Q = .. ~ ~ ~ a ,....01 =01 IiC-92 Ii! ..Q C-93 ~ Q= C-OO .• I I I I '15 .•...., '"EI o o o .. Q ii'i ex> CJ) .-o .. .. .iOI ~ S' = Q 01 .•...... S10-88 b a S11-88 S10-87 510-8 S11-87 y C6-87 C9-87 C6-88 '92 Lf C9-88 6-97 511-88 8-92 Stn B 8-93 r-l-i 8-95 8-75 8-79 ,'94 '93 S1°~k87 8-80 75 '79 '8~§0 '95 ri4 8-94 '--- C9-8 8-76 tJ) '8286"96 '9f8 8-82 .- C~~_87 '8q '90 8-85 ~ 8-84 '76 '8§7 8-83 '84 ~ 8-87 Ref. - 8-81 Lakes j 8-86 8-96 '97 rl 8-88 8-89 8-90 8-98 '----i 8-91 P3-87 8-99 P3-88 P1-87 '00 P1-88 ,P1-87 P3-87 P1-88 P3-88 Y, , , , , , 8-00 70 80 90 100 Axis I BRAY-CURTIS SIMILARITY

Figure 7. Clustering dendrogram (a) and ordination (b) of Bay of Quinte Station B and reference lake zooplankton communities (see caption to Fig. 6 for coding).

65 0.6 f-'B=-______0.8 0.5 B 50 6? -Cr E 0.7 ;;- ~ .s 0.5 "1J .~ 0.4 40 [; :S 0.6 [ S ca g> 0.4 • !It II) 0.5 o· II) 0.3 ~ .5 30 3 ::J '"E ~ 0.3 0.4 §I 0 !11: Q) I tJ :; 0.3 o· iii 0.2 20~ 0.2 0.2 5 0.1 10 iii' 0.1 0 o·00 3 o 1ll 1980 1985 1990 1995 2000 1980 1985 1990 1995 2000 2.

0.6 HB 0.8 0.8 HB 50 ::0 !It 0.7 0.7 c5" E 0.5 .s ~ 40~ 0.6 ~ :S "E 0.6 ca Ol 0.4 ~ It c S 0.5 Q) 0.5 fa. 30 (JJ --' o· :z c 0.3 • 0.4 ::J ::0 ~ 0.4 i '"Q) Dl o :; 0.3 iii 0.3 20 0.2 g. i: :;, 0.2 0.2 o 10 Qr 0.1 00 0.1 0.1 o· 3 o.o.\-,.~~~~~~~~~---.,...,....I. 0.0 0.0 .~~..;...z.._.,....,.i;CI.~~;L,_~~~;::.,:;~..j. 0 1ll 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 2.

0.6 C 1.0 0.25 C 0.9

0.8 0.20 "i E 0,0.15 ~ :z c E 0.10 '"o ~'" 02 iii p 0.05 0.1

0.00 "~.Qi,l~..u,l.~O""~O':::' __.....:;..~.,....I. 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000

Figure 8. Trends at three sites in the Bay of Quinte: Belleville (B), Hay Bay (HB), and Conway (C), in time-weighted mean (Ol-May - 06-0ct) estimates of: Left panels: mean c1adoceran length (a ), mean crustacean zooplankton length (. ), ratio of maximum predatory to total zooplankton biomass ( 0 ), ratio of realistic predatory to total zooplankton biomass (0), dotted line is proposed optimal length (Mills et al. 1987). Right panels: total biomass (a), total Daphnia biomass (e), and ratio of large/small Daphnia biomass ( 0 )

66 0.7 Herbivore Biomass

0.6 --- E 0.5 Cl -~ 0.4 ro E o 0.3 co 0.2

•• • • •••• • • ••• .. · \ .." •• • O.O~~~~~~~~~~~~~~~~~~~"•• 1975 1980 1985 1990 1995 '. 2000

Half of Cyclopoid Copepods +Adults 0.10

..,", .... \ ,--- E Cl -(/) (/) ro 0.05 E o a:i ""'"":"" .,.,,,.,,,,/'\ ,

\.T

0.00 ·h~~~~~~"'--'~~~--'-'-~~-.---r-r-'--~ 1975 1980 1985 1990 1995 2000

Figure 9. Trends in the biomass of herbivores (herbivorous cladocerans, herbivorous calanoids, all nauplii and half of the cyclopoid adults and copepodids) and carnivorous cyclopoids (half of the cyclopoid adults and copepodids)at three sites in the Bay of Quinte: Belleville (--), Hay Bay ( ...... ), and Conway( ....• ...... ).

67 Belleville Hay8ay 100 100 90 90 80 ~\~ I\~! 80 A J *'+ . ~ .. 70 70 '; /\,'\ ~ I "A--p Q) .. Q) <' ~ ¥ • ., OJ 60 Cl 60 ~ ~ Q) 50 Q) 50 e r= Q) 40 40 a. Il. 30 '" 30 • • h . ,'4-- "'-"\. 20 ~ ,,~\ I ,~ 20 I' '\N /\1\ I'- ~V~ "'j 'i. \ 10 \f"\-r ~t.. 10 ~~ , 0 ·'T-T-r-r-;,.· t- t- oo 00 00 O'l O'l O'l O'l t­ co co 0> '" O'l O'l O'l O'l O'l O'l '"O'l '"O'l O'l O> 0> 0> ~ 0> ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Year Year

Conway 100 90 80 -- %Cladocer 70 Q) ---A- %Cyclopoid OJ .l!l 60 c ~- %Calanoid Q) 50 e -II-- %Velig~r5 Q) 40 Il. 30 20 10 0 LO ~ '=I" t- o O'l t- oo 00 00 O'l O'l O'l O'l O'l O'l O'l O'l O'l '"O'l '"O'l O'l ~ ~ ~ ~ ~ ~ ~ ~ Year FigurelO. Trends in the percentage of cladqcerans, cyclopoids, and ca,lanoids out of total macrozooplankton biomass. Veligers, as a percentage of crustacean + veliger biomass, is given for compariosn.

68 Appendix Table 1. Non-parametric sign test trend statistics for selected zooplankton taxa at Bay of Quinte stations B, HB and C. N = total number of non-zero (either + or -), non-tied scores for all successive pairs of years (see Methods); x = number of +ve signs; z-score = continuity-corrected z-score after Siegel (1956); trend is either increasing or decreasing (ns = ,_.' 'J no significant trend); probability indicates the probability of the Ho (sum of +ve and -ve signs not different from 0) based on Table A of Siegel (1956; after doubling probabilities for these two-tailed tests).

Variable time N x z-score trend probability interval StationB benthic cladocera 1975-2000 210 105 0.000 ns >0.999 littoral cladocera 1975-2000 276 138 0.000 ns >0.999 Bosmina longirostris 1975-2000 276 125 -1.505 ns 0.132 Chydorus sphaericus 1975-2000 276 84 -6.441 decrease <0.001

Daphnia galeata mendotae 1975-2000 276 192 6.441 Increase <0.001 Daphnia pulicaria 1975-2000 66 41 1.846 ns 0.065

Daphnia retrocurva 1975-2000 276 92 -5.478 decrease <0.001 total Daphnia spp. 1975-2000 276 118 -2.348 ns 0.019

Eubosmina coregoni 1975-2000 276 92 -5.478 decrease <0.001 Holopedium gibberum 1975-2000 21 15 1.746 ns 0.081

Leptodora kindtii 1975-2000 209 55 -6.779 decrease <0.001 Diaphanosoma birgei 1975-2000 276 127 -1.264 ns 0.206 total calanoid copepodids 1975-2000 276 126 -1.384 ns 0.166 total adult calanoids 1975-2000 253 128 0.126 ns 0.900 Leptodiaptomus minutus 1975-2000 45 40 5.068 Increase <0.001 Skistodiaptomus oregonensis 1975-2000 105 69 3.123 Increase 0.002 Leptodiaptomus siciloides 1975-2000 120 92 5.751 Increase <0.001

69 Appendix Table 1 cont'd Variable time N x z-score trend probability interval total calanoid nauplii 1975-2000 276 187 5.839 increase <0.001 .~ Eurytemora affinis 1975-2000 105 46 -1.171 ns 0.242 benthic copepods 1975-2000 136 90 3.687 Increase <0.001 cyclopoid copepodids 1975-2000 276 103 -4.153 decrease <0.001

Diacyclops thomasi 1975-2000 253 140 1.635 ns 0.102

Cyclops vernalis 1975-2000 276 103 -4.453 decrease' <0.001

Mesocyclops edax 1975-2000 276 167 3.437 mcrease <0.001 cyclopoid nauplii 1975-2000 276 166 3.311 increase <0.001

Tropocyclops extensus 1975-2000 276 136 -0.181 ns 0.856 total adult cyc1opoids 1975-2000 253 107 -2.389 decrease 0.017 StationHB benthic cladocera 1975-2000 135 80 2.066 increase 0.039 littoral cladocera 1975-2000 276 158 2.348 mcrease 0.019

Bosmina longirostris 1975-2000 276 100 -4.514 decrease <0.001

Chydorus sphaericus 1975-2000 276 78 -7.163 decrease <0.001

Daphnia galeata mendotae 1975-2000 276 230 11.015 increase <0.001

Daphnia pulicaria 1975-2000 105 70 3.318 mcrease <0.001

Daphnia retrocurva 1975-2000 276 156 2.107 increase 0.Q35 total Daphnia spp. 1975-2000 276 189 6.079 mcrease <0.001 Eubosmina coregoni 1975-2000 276 101 -4.394 decrease <0.001

Holopedium gibberum 1975-2000 231 191 9.869 increase <0.001

Leptodora kindtii 1975-2000 136 26 -7.117 decrease <0.001

Diaphanosoma birgei 1975-2000 253 134 0.880 ns 0.379 total calanoid copepodids 1975-2000 276 137 -0.060 ns 0.952

70 Appendix Table 1 cont'd

Variable time N x z-score trend probability interval total adult calanoids 1975-2000 276 176 4.514 Increase <0.001

Leptodiaptomus minutus 1975-2000 45 35 3.578 Increase <0.001

Skistodiaptomus oregonensis 1975-2000 231 185 9.080 Increase <0.001

Leptodiaptomus sicilis 1975-2000 15 10 1.033 ns 0.302·

Leptodiaptomus sieiloides 1975-2000 253 122 -0.503 ns 0.615

Limnoealanus maerurus 1975-2000 10 7 0.949 ns 0.343 total calanoid nauplii 1975-2000 276 201 7.524 Increase <0.001

Eurytemora affinis 1975-2000 105 57 0.781 ns 0.435 benthic copepods 1975-2000 45 36 3.876 Increase <0.001 - cyclopoid copepodids 1975-2000 276 104 -4.033 decrease <0.001

Diacyclops thomasi 1975-2000 276 132 -0.662 ns 0.508

Cyclops vernalis 1975-2000 276 118 -2.348 decrease 0.019

Mesocyclops edax 1975-2000 276 182 5.237 Increase <0.001 cyclopoid nauplii 1975-2000 276 156 2.107 Increase 0.035

Tropocyclops ex;tensus 1975-2000 276 95 -5.116 decrease <0.001 total adult cyclopoids 1975-2000 276 118 -2.348 decrease 0.019 Station C benthic cladocera 1975-2000 45 35 3.578 Increase <0.001 littoral cladocera 1975-2000 276 167 3.431 Increase <0.001

Bosmina longirostris 1975-2000 276 87 -6.079 decrease <0.001

Chydorus sphaerieus 1975-2000 276 100 -4.514 decrease <0.001

Daphnia galeata mendotae 1975-2000 276 215 9.210 Increase <0.001

Daphnia puliearia 1975-2000 91 66 4.193 Increase <0.001

Daphnia retroeurva 1975-2000 276 146 0.903 ns 0.367

71 Appendix Table 1 cont'd

Variable time N x z-score trend probability interval total Daphnia spp. 1975-2000 276 158 2.348 increase 0.019 .~ Eubosmina eoregoni 1975-2000 276 116 -2.588 decrease 0.010

Holopedium gibberum 1975-2000 275 221 10.010 Increase <0.001

Leptodora kindtii 1975-2000 210 67 -5.175 decrease <0.001

Polyphemus pediculus 1975-2000 35 32 4.733 Increase <0.001

Diaphanosoma birgei 1975-2000 276 136 -0.181 ns . 0.856 total calanoid copepodids 1975-2000 276 100 -4.515 decrease <0.001 total adult calanoids 1975-2000 276 122 -1.866 ns 0.062

Leptodiaptomus minutus 1975-2000 55 23 -1.079 ns 0.281

Skistodiaptomus oregonensis 1975-2000 276 166 3.311 increase 0.001

Leptodiaptomus sicilis 1975-2000 119 48 -2.017 decrease 0.044

Leptodiaptomus siciloides 1975-2000 136 84 2.658 increase 0.008

Limnoealanus maerurus 1975-2000 28 10 -1.323 ns 0.186 total calanoid nauplii 1975-2000 276 190 6.200 increase <0.001

Eurytemora affinis 1975-2000 253 97 -3.646 decrease <0.001 benthic copepods 1975-2000 10 4 -0.316 ns 0.752 cyclopoid copepodids 1975-2000 276 86 -6.200 decrease <0.001

Diaeyclops thomasi 1975-2000 276 74 -7.645 decrease <0.001

Cyclops vernalis 1975-2000 253 69 -7.167 decrease <0.001

Mesoeyclops edax 1976-2000 276 120 -2.107 decrease 0.035 cyclopoid nauplii 1975-2000 276 161 2.709 increase 0.007

Tropocyclops extensus 1975-2000 276 77 -7.283 decrease <0.001 total adult cyclopoids 1975-2000 276 74 -7.645 decrease <0.001

72 Appendix Table 1 cont'd

Variable time N x z-score trend probability interval Station B benthic c1adocera 1975-1994 120 71 1.917 ns 0.055 littoral cladocera 1975-1994 153 71 -0.808 ns 0.419

Bosmina longirostris 1975-1994 153 63 -2.102 decrease 0.036

Chydorus sphaericus 1975-1994 153 69 -1.132 ns 0.258

Daphnia galeata mendotae 1975-1994 153 123 7.438 mcrease , <0.001

Daphnia pulicaria 1975-1994 55 34 1.618 ns 0.106

Daphnia retrocurva 1975-1994 153 52 -3.881 decrease <0.001 total Daphnia spp. 1975-1994 153 67 -1.455 ns 0.146

Eubosmina coregoni 1975-1994 153 71 -0.808 ns 0.419

Holopedium gibberum 1975-1994 6 4 0.408 ns 0.683

Leptodora kindtii 1975-1994 104 35 -3.236 decrease 0.001

Diaphanosoma birgei 1975-1994 153 61 -2.425 decrease 0.015 total calanoid copepodids 1975-1994 153 91 2.264 mcrease 0.024 total adult calanoids 1975-1994 136 81 2.144 mcrease 0.032

Leptodiaptomus minutus 1975-1994 45 40 5.068 mcrease <0.001

Skistodiaptomus oregonensis 1975-1994 45 36 3.876 mcrease <0.001

Leptodiaptomus siciloides 1975-1994 78 56 3.737 mcrease <0.001 total calanoid nauplii 1975-1994 153 94 2.749 mcrease 0.006

Eurytemora affinis 1975-1994 78 42 0.566 ns 0.571 benthic copepods 1975-1994 78 58 4.189 mcrease <0.001 cyc1opoid copepodids 1975-1994 153 89 1.940 (ns) 0.052

Diacyclops thomasi 1975-1994 153 113 5.821 mcrease <0.001

Cyclops vernalis 1975-1994 153 74 -0.323 ns 0.747

73 Appendix Table 1 cont'd

Variable time N x z-score trend probability interval

Mesocyclops edax 1975-1994 153 101 3.881 Increase <0.001 .~ cyclopoid nauplii 1975-1994 153 83 0.970 ns 0.332

Tropocyclops extensus 1975-1994 153 71 -0.808 ns 0.419 total adult cyclopoids 1976-1994 153 81 0.647 ns 0.518 StationHB benthic cladocera 1975-1994 104 72 3.824 Increase <0.001 littoral cladocera 1975-1994 153 86 1.455 ns 0.146

Bosmina longirostris 1975-1994 153 61 -2.425 decrease 0.015

Chydorus sphaerieus 1975-1994 153 62 -2.264 decrease 0.024

Daphnia galeata mendotae 1975-1994 153 131 8.731 Increase <0.001

Daphnia puliearia 1975-1994 66 48 3.570 Increase <0.001

Daphnia retroeurva 1975-1994 153 93 2.587 Increase 0.010 total Daphnia spp. 1975-1994 153 107 4.851 Increase <0.001

Eubosmina eoregoni 1975-1994 153 69 -1.132 ns 0.258

Holopedium gibberum 1975-1994 120 98 6.847 Increase <0.001

Leptodora kindtii 1975-1994 66 11 -5.293 decrease <0.001

Diaphanosoma birgei 1975-1994 136 65 -0.429 decrease <0.001 total calanoid copepodids 1975-1994 153 52 -3.881 decrease <0.001 total adult calanoids 1975-1994 153 92 2.425 Increase 0.015

Leptodiaptomus minutus 1975-1994 45 35 3.578 Increase <0.001

Skistodiaptomus oregonensis 1975-1994 120 99 7.029 Increase <0.001

Leptodiaptomus sicilis 1975-1994 10 8 1.581 ns 0.114

Leptodiaptomus sieiloides 1975-1994 136 72 0.600 ns 0.549

Limnoealanus maerurus 1975-1994 10 7 0.949 ns 0.343

74 Appendix Table 1 cont'd

Variable time N x z-score trend probability interval total calanoid nauplii 1975-1994 153 88 1.779 ns 0.075 .~ Eurytemora a.!finis 1975-1994 66 37 0.862 ns 0.389 benthic copepods 1975-1994 28 21 2.457 Increase 0.014 cyclopoid copepodids 1975-1994 153 82 0.808 ns 0.419

Diacyclops thomasi 1975-1994 153 86 1.455 ns 0.146

Cyclops vernalis 1975-1994 153 80 0.485 ns . 0.628 Mesocyclops edax 1975-1994 153 100 3.719 Increase <0.001 cyclopoid nauplii 1975-1994 153 87 1.617 ns 0.106

Tropocyclops extensus 1975-1994 153 53 -3.719 decrease <0.001 total adult cyclopoids 1975-1994 153 66 -1.617 ns 0.106

Station C benthic cladocera 1975-1994 36 26 2.500 Increase 0.012 littoral cladocera 1975-1994 153 96 3.072 Increase 0.002

Bosmina longirostris 1975-1994 153 73 -0.485 ns 0.628

Chydorus sphaericus 1975-1994 153 43 -5.336 decrease <0.001

Daphnia galeata mendotae 1975-1994 153 123 7.438 Increase <0.001

Daphnia pulicaria 1975-1994 78 59 4.416 Increase <0.001

Daphnia retrocurva 1975-1994 153 89 1.940 (ns) 0.052 total Daphnia spp. 1975-1994 153 96 3.072 Increase 0.002

Eubosmina coregoni 1975-1994 153 90 2.102 Increase 0.036

Holopedium gibberum 1975-1994 152 105 4.623 Increase <0.001

Leptodora kindtii 1975-1994 136 41 -4.545 decrease <0.001

Polyphemus pediculus 1975-1994 20 17 2.907 Increase 0.004

Diaphanosoma birgei 1975-1994 153 68 -1.294 ns 0.196

75 Appendix Table 1 cont'd

Variable time N x z-score trend probability interval total calanoid copepodids 1975-1994 153 60 -2.~87 decrease 0.010 total adult calanoids 1975-1994 153 61 -2.425 decrease 0.015

Leptodiaptomus minutus 1975-1994 45 14 -2.385 decrease 0.D17 Skistodiaptomus oregonensis 1975-1994 153 87 1.617 ns 0.106

Leptodiaptomus sicilis 1975-1994 90 43 -0.316 ns 0.752

Leptodiaptomus sieiloides 1975-1994 91 59 2.726 increase' 0.006 Limnoealanus maerurus 1975-1994 15 3 -2.066 decrease 0.039 total calanoid nauplii 1975-1994 153 87 1.617 ns 0.106

Eurytemora afjinis 1975-1994 136 46 -3.687 decrease <0.001 benthic copepods 1975-1994 10 4 -0.316 ns 0.752 cyclopoid copepodids 1975-1994 153 81 0.647 ns 0.518

Diaeyclops thomasi 1975-1994 153 41 -5.659 decrease <0.001

Cyclops vernalis 1975-1994 136 48 -3.344 decrease <0.001

Mesoeyclops edax 1975-1994 153 66 -1.617 ns 0.106 cyclopoid nauplii 1975-1994 153 101 3.881 mcrease <0.001 Tropoeyclops extensus 1975-1994 153 64 -1.940 (ns) 0.052 total adult cyclopoids 1975-1994 153 55 -3.396 decrease <0.001

76 Appendix Table 2. Mann-Whitney V-test values testing the null hypothesis for each species or taxon group that there is no difference in density between the 6-year pre- and post Dreissena time periods (1989-1994 vs 1995-2000). Those values with an asterisk indicate a probability of ~95 % for rejection of the null hypothesis (i.e. a strong likelihood of significant difference). .~

Mann-Whitney V-value

Station B StationHB Station C benthic cladocera 11.5 12 17.5 littoral cladocera 8 13 18

Bosmina longirostris 7 17 7

Chydorus sphaericus 5* 5* 15

Daphnia galeata mendotae 15 14 17

Daphnia pulicaria 8 9.5 4.5*

Daphnia retrocurva 18 14 17 total Daphnia spp. 17 18 16

Eubosmina coregoni 7 10 6

Holopedium gibberum 14 2* 2*

Leptodora kindtii 13 8 15

Polyphemus pediculus 15 18 18

Diaphanosoma birgei 14 10 14 total calanoid copepodids 10 6 17 total adult calanoids 16 14 12

Leptodiaptomus minutus 12 9 13.5

Skistodiaptomus oregonensis 14 11 9

Leptodiaptomus sicilis 18 17.5 8

Leptodiaptomus siciloides 15 17 15.5

77 Appendix Table 2 cont'd

Limnoea/anus maerurus 15 15 12 total calanoid nauplii 9 2* 2*

Eurytemora affinis 16 10.5 11 benthic copepods 18 14 18 cyc1opoid copepodids 5* 8 0* Diaeyclops thomasi 7 15 18 Cyclops vernalis 17 15 14 Mesocyclops edax 18 13 14 cyclopoid nauplii 11 14 15 Tropoeyclops ex;tensus 15 16 8 total adult cyclopoids 13 15 15

78 Appendix Figure 1

May 1 OctS

abc d e f g h k A I I - 1 ,,/ , I 1 1 I I I 81 182,83,841 S5 I sa I S7 I S8 I I S10 I I 12 ~,.' ~'~I~I ..- I I I I , I I~I~I~I r r I r T T r I JLiI . Aug;' Sep; ; Oct (1) (15) (29) (12) (25) (10) (23) (8)

May 1 OctS B b c d e f g h , I 81 ,82 , 83 1 54 • SS S7 S8 S9 S10 tit r r r E • ! r r r r Apr; May Jun Jul Aug Sep Oct; (22) (12) (4) (25) (6) (23) (13) (3) (25) (19)

Appendix Fig. 1. Pictoral representation of the method used for time-weighting sample results over the May 0 I to October 06 time period for each year. The second example (B) hru both earlier and later sampling dates for comparative purposes. The astereisks (*) represent dates for which sample results (sl, s2, s3, etc.) are available (for (A), May 6, May 20, June 3, etc.) . The vertical dashed lines (a, b, c .... k for (A) and a-i for (B» represent date values for the mid-way points between the sampling dates.

For (A), the May I - Oct 6 time-weighted mean =

sl *(a-May I) + s2*(b-a) + s3*(c-b) + s4*(d-c) + sS*(e-d) + s6*(f-e) + s7*(g-f) + sS*(h-g} + s9*(i-h) + sIO*G-k) + sll*(k-j) + sI2*(Oct 6-k)]/Oct 6-May I

For (B), the May I - Oct. 6 time-weighted mean =

sl *(a-May I) + s2*(b-a) + s3*(c-b} + s4*(d-c) + sS*(e-d) + s6*(f-e) + s7*(g-f) + sS*(h-g) + s9*(Oct 6-h)]/Oct 6-May 1

L Oct 6-May 1 = datevalue for Oct 6 minus datevalue for May 1 (the total number oj days between May I and Oct 6) 2. The Oct sample in (B) has no weight in this case because the half-way point between it and the September 2S sample occurs after the October 6 cut-off.

79 Appendix Figure 2

A B Quinto Station HB Quinte Station HB ChydofUS sphsericus total cyclopoid copepodids

800

~ c: ~ 600 ~ 0" c: ~ ~ U. 400 I 400

200 H.

o i pf+", ~ -0.65 -0.55 -0.45 -0.35 -0.25 -0.15 -0.05 0 -0.15-0.10-0.05 0 0.05 O. 0.20 Bootstrapped Mean Bootstrapped Mean

Appendix Fig. 2. Frequency distributions of the bootstrapped means of sign test results for two zooplankton taxa from Station HB. The sign test null hypothesis (Ho) states that there is no significant difference between the number of

positive and negative signs (i.e. mean = 0). In this example, for Chydorus sphaericus (A), the zero mean is well outside the bias-corrected 95 % confidence interval around the bootstrapped mean of -0.434, indicating that it is very unlikely that there is no difference between the sum of positive and negative signs (i.e. is a strong likelihood of a negative trend). For total cyclopoid copepodids (B), no significant trend was determined, because the zero mean was well within the bias-corrected 95 % confidence interval around the bootstrapped mean of +0.029.

80 Appendix Figure 3

a b '" C 20"_:::--;;- ____) e-e Sin B • .-. Stn B • .-. Sin B t "'~~.t.. Stn HB " 400 ..... " StnHB ~ o A--& Sin HB • E 30 ," ' o ~ u; 0-0 Sin C t t 0-0 StnC o g !:. 15 I 0-0 StnC " " ~ " o " "' 300 " " l!! :::. ," ' " " "' 20 , ' ~ .g , , , " " .'.J. ,:~. ~ f " 200 \\, 10 i : ~ ~ ... .g . ~ II' j':'.\:::• I,' " ,. 'A" ',A , I' ".' "o '0 , ' '~, "0 '" ~ ~, ,", : : ... ..!!! 10 , .-~..... , , ~ .; /\~ . :::, , , A";, ;S" 100 ·1: :: ,.\ .1, \V' \/1 5 " , e " , . ~ 1'! " j • .\ ::, , •.•.• . "'"~:. ~ 1 / . • 'I 0 o • t ~,"'" III" •/ e'''', " / .!J! ': ~ I. '. ,j\. l\)Al'J;:.: ..:,l:/ O~~ •. ~ .~. ~-V ~ o~ ~:I!! "u F ~;!O.O.~~~~.O~;o!NI:i:;A.,;.~ OJ , •• l:o~~.o.O-~.O·D-o.r:rD'AA.,ff ' -rJ\"u. 19'75 19'80 19'85 19'90 19'95 20'00 i 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 Year Year , Year d e f 40 .-e Stn B h· .-. Sin B .-. Stn B ... ~ ... Sin HB .6.--.6. Stn HB , , ~E 30 A SlnHB 0-0 Stn C , , 0-0 Sine · .... ~E 600 '" • 0-0 Stn C .:, :, ~ 30 ~ . g 1\ . • I' " I' .~ " ~ " o I' I' .' i, " ! "/';..\ " 1r I. I' .. :::. ., , " ,,\t ;}0'" ...... ~ 400 " ." "S ~ " 20 ~ 20 ,i '·'···Xi.:', '/ '\ :" ; \ "- , , ~ !\V\n \~' :, .\: , .~ , , .:::o :, "'~':' ~ ~ ., ,' .!J! \ Q) • , ' , ''. ' ~ , I .... .g . ! \/0 '~\'\, ~ "I' -& 200 i .~:i: g 10 1 •.• -. : ¥ / .. ~ ~.~ Ii : I.: " ,,, ", 10:: "~~ "/\'r .,' " I '-("/V; '," ~ :~: ~ ~ i 'iii • A. ' ,,,, .,' Q ~~~ \ ~ ~ ~ " e.i!•• " _ -e 1 :JVN-\vlJ\j\~ 0-1 a-a I!!.e.,. ••• -A -o-.-..t'i-. ~ o "u ~if 0 0' "u 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 Year Year Year

Appendix Fig. 3. Time-weighted mean densities (May 1 - October 6 for each year) of several cladocerans at the three Bay of Quinte sampling stations, 1975-2000. Littoral cladocerans includes Pleuroxus denticulatus, Acroperus harpae, Simocephalus serrulatus, S. vetulus, Diaphanosoma brachyuran, all Ceriodaphnia spp., Ophryoxus gracilis, Camptocercus rectirostris, Leydigia quadrangularis, Latona setifera and Sida crystallina. Benthic cladocerans include all Alana species, Eurycercus spp. and Ilyocryptus spinifor.

81 Appendix Figure 4 a b • -. Sin B • c ~ a-e Sin B ~ • t ~ a-. Stn B : J.--.I.. Sin HB . ~ 300 ... .f.--. StnHB ~ 100 .--J. Stn HB!: 0-0 SlnC .. 80 .. ~ 0-0 g .. o .0-0 StnC o SlnC ;: o .. o · o , , .. o o 80 , , .. ~ ::. .. r, .,\ •.• ::. , , .. ::::- 60 " CI) : : 200 :" : :\, . ~ : ~ t I .. 8, •., I ",P ,1.\ .g 60 :f~:: . , ." , ,' , , ...... f:' " Ie 'I. '.... • g> , , , , ' t : : - ~ Q I. , ' ~ 40j '\ -[ 40. ~ .• :V).. A 100 t .s ",,\ .i \! \i \ ,~ '" '~Io.,,: ':'!J ...\ :'''''V''..., .. Ct) " ;. ... "'. "* ·S ~ \ ::::. 'J. , '" E .,,:' .. /\/. :, ~ A' ' ,,~.j: "'\ ,- . !' :, '" 20 , ' A "" , , 1> •• o 1 • '.. II ' Ii.. J.':' " ' A , , : , -g ! 20! .J .. ~~t~.i\'.:l J ! ~ "',"tr· w,····:;~\"-~;:;I.l.o "'. lti -<:: , ;\. ~~if· ..l ... I o~.jV.o·j\.o::"-o.::if'~ (,) a 0-0 o-o-O'o-D-a-o·Q·o-aAo-O'CHJ_O_ ., oJ •.. o "-0 .'_- --'-- ._'-- --'-- ._'-- --'. 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 I "f 0 I ,,~u 1 ,,~o 1990 1995 2000 d Year Year f I . Year I ._. Stn B e • e-. Stn B t .-. Sin 8 5j .... Stn HB ~ ...... Sin HB 400 .~~. Stn HB 0-0 Sin C • @. 600 0-0 Sin C .. 0-0 Stn C lo ,:;- 1 4 .. E •i ::. E " %300 A <: • ..1l 400 t ~ \ t, ( \ ~ " ·S } 31\ " • .,,' . " -" 200 E'" 2 . .. l' . I· ," , l!! . I\ "" : ' . ~. ! .~ b • , , ~ ~ ~ 200 , , \t'~ '. lii 1 j , \i\'\ iN" .,... g. , , . ~100 ·V: ~\, " , , '" I . • I.~'. ~: :~': -.J £ '\ ' " '1\ ~. -& I ...... : "I ~ •,01; I- '. ,. • : ..... ~ .... .!1! ~ "u fb.o-,": . Q oj "u o_~~i/\ o~-y-~~o.o.~:o-o-if\ ~o ~" •• i!\~:- < • ~.~.' ~ ... "_-~'ii..:[~:g_._~_!:g_",,-'._._ "I •. "_.I~, 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 19"75 Hi80 19'85 19'90 H195 2000 Year Year Year

Appendix Fig. 4. Time-weighted mean densities (May 1 - October 6 for each year) of several c1adocerans at the three Bay of Quinte sampling stations, 1975-2000,

82 Appendix Figure 5

a ~ b SIn B I e-. StnS • .-. . '"E 4 • A--A SIn HB I "

Appendix Fig. 5. Time-weighted mean densities (May 1 - October 6 for each year) of total nauplii (a), copepodids (b) and adult calanoid copepods (c) at the three Bay of Quinte sampling stations, 1975-2000.

83 Appendix Figure 6

a b i.------~ C ! e-e Sin B • ill-ill Stn B ill-ill Stn B t .. 120j .--. Stn HB .... ~ ... Sin HB ~E .. "i '" 40 : • -~ ... Sin HB " # ~ 0-0 SlnC 0-0 SlnC " .." !.600 0-0 Stn C ".. ~ 100 ~ :: co " .." ~ ." : '5 ~ 30 .. '0 .5; 80 ·11 :: ., : E :, 400 : "ill ., ~ ... ~ , •, I , ., ,' t " 60 o 20 ., .. ~ :~ !l " , , ~ 1:t !l I g. 40 o ,'",:1::1'& :: , '" " ~200 :~ : ." ; ~. '\ .., :'., loll , , " " ', ' :g . ~ , " .. "..... J , , ... ~,',,: ~ " I' , 1 Q. : :J' \ :..-\ 10 , , " " ~ 20 \ , " ".0 " ~ ! ..... • '. • 0 '" -,.q :: \ : I, "-0.:;.', : ~ • ~.\ ;\ ~ I /: • ..... oi o~ ..i -.... .-•. ~.•.•.•.•.• -.-.-.-.-.-.-.-.-•. -.-a·., Oi~ o:~ ~ifj.6.-', i A, !.ttL.-.-.,_ ' ~;~~:. L1Jj~ 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 Year _d , e Year f Year ~ i e-e Sin B , ill-ill Stn B E , • • ill-ill Stn B ... ~~ ... SlnHB .' !.800 .' .. 30~ .--. Stn HB 300 .... - ... StnHB ·21 0-0 Sin C .' 0-0 Sin C 0-0 Sin C .' ~., E ~ ·.' . 2 !. i5 600 · . 2 ·21 • · . 20 ~ 200 1il' · . l;l (; · . E ; · ' .' ! '" , ~ 400 · . ~ " t; :: e! · ' ,• c:: " E ·, .' .' \ .' ~I :: ~ ' ' .' ..!l! 10 .. " :\ a ~ " ~ 100 .. . t ,g 200 1\ ' .'.' () .' " , ' . I ... ~ " c:: ":: "'f I' '. ,] () :' -"/ • .§ j! :::: :. .. ·21- !:;, '. \/ ' ..... Ii. :·~e-.i ~ ~ c}j • _0_0·0'0 " o ii'i ~.r-:.o ~"'~-O~f 0,.-- .,M:-i-.-~6• .L.-.- •. L.~.. I.J.-. Oi-~ ~~<.~~ 1975 1980 1985 1990 1995 2000 19'75 1980 1985 1990 1995 2000 1975 1980 1985 19~u l~~:> ~uuu Year Year Year

Appendix Fig. 6. Time-weighted mean densities (May 1 - October 6 for each year) of six species of calanoid copepods at the three Bay of Quinte sampling stations, 1975-2000.

84 Appendix Figure 7

a b 25,~------~ 0 0-0 Stn B 0-0 Stn B .. ~-. StnHB ~ 400 0-0 Stn C 1o 20 " o ~ ~ ~ 300 '"o -g'" 15 "a. g- o. 8.o o 200 S 10 •, o '0" :2 a. ,, ~ 100 o 5 : co U ~

1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 c Year Year ~ d ~------~ ~ 100 0-0 Stn 8 0-0 Stn B ~ ~ 70 t •..• SIn HB A- -.t.. Stn HB ;t :~ ~ .. , 'I 0-0 Stn C t g 60 a-aStnC: '. :: t g 80 \ ,.- I , r 1 " o " -;;; , ~i.::: t " :s ," , 50 'r, " , ""C :: I " , , C. 60 , , =g ,.': ::: ::> , , 0.40 l .::: . 20 0 ./ (\../l('>v /\1\ o 0 0V • ,,OJ:' ....• P\ t-h;':~ ;~ \ ~ .... 0 • • ....\. 0; i D ~~ ~ 0'0 o 1 0 u • o..~~ct. \ -0 0·0 m • ~~ - 0 B 1975 1980 1985 1990 1995 2000 01975 1980 1985 1990 1995 2000 Year Year

Appendix Fig. 7. Time-weighted mean densities (May 1 - October 6 for each year) offour cyclopoid copepods groups at the three Bay of Quinte sampling stations, 1975-2000. Benthic copepods include Eucyclops agilislserrulatus and E. speratus.

85 Appendix Figure 8

a o e-e Stn B 4 .--. Stn HB 0-0 Stn C

3 4 2 3 ! A 2 l .:....!: I" .l '\ 1 / .. e .• ,'\ e,:.,: "~' ~\.• f."'.,l 4~ It.. 1\ t It. ~ ~ ,.... I ... ' '\ , A'" • ...... :..... /lye,' 1.;: .... o ...... ~ ...... ,...... " '. .~' .-...... -~~ o 0'0 6'D-O.o.O-o.o.o·o-o.o.o-O.~;t:II.~-O_D_O_II':~ 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 Year Year c d.,------~ e-. Stn B • ~ .-e Stn B t 5 .--. Stn HB ~ 14 I.". Stn HB :: 0-0 Stn C o 0-0 StnC " g 12 , , 4 0) 10 , , •, , . , ' , , ' 3 , , 8 , , ' ,\1 !, " ~ , ' A " ' ~, , ' ~ " ", I ... " ", I I 2 I \ ,.L J , I "'/'" , 64 • m"\ . .-( k~!':" :! .\: " ; " : : :~ ~ :'. 11 .\~ ~: /!.... 4 e-.!. I./~/ .f.,4~~ i\ i e 2!~ ~:w:~/ \~ '1),1\ ;.~. 0-'~ "-O-o.d o~_~~;;,p-o_o-"u_o_. o f 'e·· • • ,..... ~*~~~ 1975 1980 1985 1990 1995 2000 1975 1980 1985 1990 1995 2000 Year Year

Appendix Fig. 8_ Time-weighted mean densities (May 1 - October 6 for each year) of four cyclopoid copepod species at the three Bay of Quinte sampling stations, 1975-2000.

86