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Zooplankton Production Wetzel, Chapter 16 Pages 468-482 Zooplankton Production, General Concepts • Net Productivity – sum of the growth increments of all specimens of the populations • P = C – F – U – R – G; where P = production, F = egestion, U = excretion, R = respiration, and G = gametes • NOTE: this is Net Production, not Gross Production Zooplankton Production, General Concepts, continued • To measure Production we need: – Distribution of organisms – Stages of development and ages – Development times • These ALL vary among species, seasons, changing environmental conditions • Frequency of sampling MUST be shorter than generation times of organisms • Consequently, Production is easy to measure in organisms with long lives and short reproductive bursts but difficult to measure in organisms with short lives and continuous reproductive bursts P/B Ratios • This measure is the ratio of Production to Biomass • B = measure of biomass of population – Units – mass per unit area (or volume) – Represents a “storage” of mass or energy • P = measure of production of a population – Units – mass or energy per area per time – Represents a “flux” or “flow” of energy or mass P/B Ratios continued • Therefore, P/B = mass/area/time divided by mass/area = 1/time = Turnover Rate • This Turnover Rate is an estimate of the replacement of a population and is used for comparisons among species and different environmental conditions • 1/P/B = B/P = time = Turnover Time • Turnover Time = average duration of the life of a species P mass / area / time 1 TurnoverRate B mass / area time Turnover Times • Times vary for different classes of organisms in different lakes under varying environmental conditions • Wetzel Table 16-18 Factors Contributing to ZP Productivity • Temperature • Food Resources – Primary Productivity – Bacteria – Detritus • Body Size • Algal Productivity itself may not be sustainable for all ZP productivity – Productivity supplemented by bacterial and detritus web • Major loss of organic matter to decomposition without consumption Factors continued • Wetzel emphasizes the non-predatory, detrital food-webs and how productivity is lost to these other webs • Wetzel Fig 16-41; notice productivity estimates by trophic status Productivity in Ecosystems • Varying conditions influence changes in productivity – Temperature, food quality, etc. – Spring biomass max. follows algal bloom – Productivity lags behind biomass • Wetzel Fig 16-43 Productivity in Ecosystems cont. • Rotifers contribute significantly to productivity (energy cycling) – Small size but quick turnover times • Wetzel Table 16-22 Productivity in Ecosystems cont. • Productivity can also demonstrate the structure of inter-specific competition • Position of species’ niches distributed in time and space but also in relation to food, predators • Allows coexistence of limnetic zooplankton • Wetzel Fig 16-44 Productivity in Ecosystems cont. • Transfer Efficiency – ability to pass energy up trophic web • 10% of Production of lower trophic level is passed up to the next higher level • Wetzel Table 16-25; NOTE rows Production and Decomposition Losses Conclusion • Differences and similarities between biomass & production • How zooplankton production is dependent on features of the ecosystem • Interaction among zooplankton and both lower and higher trophic levels