Evaluation of Optically Acquired Zooplankton Size-Spectrum Data as a Potential Tool for Assessment of Condition in the Great Lakes

Abstract

An optical plankton counter (OPC) potentially provides an assessment tool for zooplankton condition in ecosystems that is rapid, economical, and spatially extensive. We collected zooplankton data with an OPC in 20 near-shore regions of 4 of the Laurentian Great Lakes. The zooplankton size information was used to compute mean size, biomass density, and size-spectra parameters for each location. The resulting metrics were analyzed for their ability to discriminate among the Great Lakes. Biomass density provided discrimination among lakes, as did several parameters describing spectra shape and distribution. A proposed zooplankton indicator, mean size (determined with OPC measurements in this study), was found to provide discrimination among lakes. Size-spectra-related parameters added increased ability to discriminate in conjunction with the biomass density (or mean size) metric. A discriminant function analysis of the multiple metrics (mean size, biomass density, and distribution parameters) suggests that a multi metric size-based approach might be used to classify communities among lakes improving a mean-size metric. The feasibility OPCs and size-based metrics for zooplankton assessment was found to have potential for further development as assessment tools for the biological condition of zooplankton communities in the Great Lakes.

Ecological change in Great Lakes communities — a matter of perspective

“…Gamble et al (2006) point out that the general similarity in size spectra noted for a wide range of ecosystems indicates a "basic underlying ecosystem condition or pattern". In a similar study, Yurista et al (2005) were successful in discriminating zooplankton assemblages among Lakes Superior, Michigan, Huron, and Erie based on statistical descriptors of zooplankton biomass domes. It is not unexpected that differences in size structure may be observed when lake features such as productivity or morphometry differ substantially, but it must be cautioned that the Yurista et al (2005) analyses were based on very limited spatial and temporal sampling, so that the mean state of these systems may not have been adequately quantified.…”

Lake Superior zooplankton biomass: Alternate estimates from a probability-based net survey and spatially extensive LOPC surveys

“…The alongshore towing at a 20-m contour was continuous day-night. LOPC tows were all conducted during the seasonal peak sampling window (midJuly thru mid-September, Yurista et al, 2005) and from the vessels R/V Lake Explorer LOPC biomass data (ESD N 150-μm to 5-mm particles, which excludes Mysis-sized organisms) was compiled across the years into one large file (1.15 M records) and a Kriging estimate made for regularly spaced grid points of 5-m intervals across bottom depth and 1-m intervals across the depth profile (Isaaks and Srivastava 1989;SURFER 2002). This resulted in a collapsing of positional reference data (four dimensions; latitude, longitude, bottom depth, sample depth) onto the two dimensions of bottom depth and sample depth.…”

“…For example, distribution patterns (Kerfoot et al, 2007), particle transport (Zhou et al, 2001), or general relationships (Yurista et al, 2005) have produced significant understanding through relative comparisons. For monitoring, there is an expectation that the results are realistic, consistent, and can be compared among and between other methodologies and environments.…”

The use of the Laser Optical Plankton Counter to measure zooplankton size, abundance, and biomass in small freshwater lakes

“…It has been used in a variety of marine environments (Huntley et al 1995, Grant et al 2000, Remsen et al 2004) and large inland lakes (Sprules et al 1998, Yurista et al 2005), but to date, the use of the OPC in small freshwater lakes has been limited. Gal et al (1999) used the OPC to examine the distribution of large Mysis relicta, but did not examine the smaller, more numerous zooplankton.…”