Composition, size, and biomass of zooplankton in large productive Florida lakes

Abstract

Crustacean zooplankton data were compiled from long-term observational studies at seven large shallow Florida lakes, to determine whether there are general characteristics in regard to species composition, body size, and biomass. In particular, we examined whether patterns in body size and species richness fit empirical models developed by Stanley Dodson. The lakes included range in size from 125 to 1730 km 2 and encompass mesotrophic to hyper-eutrophic conditions. We found that zooplankton biomass was strongly dominated by one species of calanoid copepod-Arctodiaptomus dorsalis. Large daphnids were absent, and Cladocera assemblages were dominated by small taxa such as Ceriodaphnia, Chydorus, and Eubosmina. The total number of species of pelagic cladocerans (8-12) was consistent with Dodson's predictions based on lake area. The average size of crustacean zooplankton in Florida lakes is small in comparison with temperate communities. A. dorsalis is the smallest calanoid copepod in North America, and the mean length of Cladocera (0.6 mm) is consistent with Dodson's results that size decreases from temperate to tropical zones. Total biomass of crustacean zooplankton was very low, ratios of zooplankton to phytoplankton biomass (0.01-0.1) are among the lowest reported in the literature, and the zooplankton displayed short-lasting early spring peaks in biomass. Cladocera were almost entirely absent in spring and summer. Factors known to occur in Florida lakes, which appear to explain these characteristics of biomass, include intense fish predation and high summer water temperature.

Response of Zooplankton to Climate Variability: Droughts Create a Perfect Storm for Cladocerans in Shallow Eutrophic Lakes

“…In the case of fish predation, we know that these lakes have some of the highest recorded densities of omnivorous and planktivorous fish [15,16], and that their intense predation is largely responsible for the very low zooplankton to phytoplankton ratios and lack of large Daphnia in Florida and other subtropical lakes [1,2]. Simply by having the same number of fish concentrated with their prey in 30% to 81% less water volume could explain the changes in zooplankton, as cladocerans are highly sensitive to fish predation compared to copepods [28], in particular the dominant and relatively small species in Florida lakes, Arctodiaptomus dorsalis, which has the ability to avoid predation by executing rapid escape maneuvers [2]. In Lake Griffin, which was subjected to shad harvesting between 2000 and 2010, the highest zooplankton peaks, dominated by cladocerans, happened when shad catch per unit effort had been substantially reduced [29].…”

“…Data were obtained from six lakes (Figure 2) located in the Upper Ocklawaha River Basin, north of Orlando, Florida, between 28°55′ N 81°50′ W and 28°34′ N 81°33′ W. The lakes are shallow, with mean depths ranging from 1.4-3.4 m, and ranging in size from 5-127 km 2 (Table 1). The lakes are eutrophic, with total phosphorus (TP) from 38-131 µg L −1 , total nitrogen (TN) from 1.8-4.7 mg L −1 and chlorophyll a (Chl-a) from 35-115 µg L −1 .…”

“…All of the lakes are strongly dominated by filamentous and colonial cyanobacteria that attain exceptionally high biomass, i.e., blooms [13], and some lakes have displayed downward trends in nutrients and Chl-a, attributed to nutrient-control programs in the watershed [13,14]. The lakes all have high densities of omnivorous fish [15,16], which is typical for lowland subtropical lakes [2,17,18]. Conceptual diagram of the predicted effects of variation in climate and rainfall on drought and water depth in the shallow study lakes; the concentration of fish and nutrients in reduced lake volumes; the increased biomass of cyanobacteria in shallower nutrient-enriched water; and the increase in biomass of copepods relative to cladocerans.…”

“…Zooplankton dynamics in subtropical lakes are affected, as in other geographic regions, by a myriad of factors, including fish and invertebrate predation, food resource quantity and quality, temperature, stratification, abiotic seston and other attributes of water quality [1][2][3][4]. Conditions external to the lake, including rainfall, air temperature, wind velocity, and loading of nutrient and sediments, can affect those factors either directly or indirectly, as can characteristics within the lake such as bioturbation of sediments by invertebrates and fish, and nutrient uptake by vascular plants [5].…”

Phosphorus release of metazoan zooplankton in two bays with different trophic status in Lake Taihu (China)

“…However, nutrient excretion by zooplankton may also affect the supply and stoichiometry of nutrients and thereby influence phytoplankton and lake trophic status (Lehman, 1980a;Elser et al, 1988;Sterner and Hessen, 1994;Kowalczewska-Madura et al, 2007). The role of zooplankton has been well studied in temperate lakes, but and less so in tropical and subtopical systems where zooplankton are smaller and likely to be less efficient in grazing phytoplankton (Jeppesen et al, 2010;Havens and Beaver, 2011). However, small zooplankton exhibit high P release rates and may thus play a significant role in nutrient cycling in tropical and subtropical lakes (Pinto-Coelho and Greco, 1999).…”