| Summary: | Estimating the efficiency with which energy is transferred to higher trophic levels demands estimates of adult and juvenile copepod biomass production rates. Adult rates (egg production) are well studied; however. our knowledge of how juvenile biomass production rates (BPR) vary in situ remains incomplete and has been limited by difficulties associated with measuring somatic growth rate in the field. This problem may be resolved with the application of new methods that either: a) directly estimate BPR without additional estimates of growth or biomass, and/or: h) improve estimates of development and growth rate that may then be applied to estimates of biomass. The objective of this thesis is to develop a routinely applicable method that may be used to gain greater insight into how production of juvenile copepods is regulated in the field. I have developed a field method for estimating BPR, development and growth of marine copepods that is based on measuring the in situ rate of decay of the crustacean moulting enzyme, chitobiase. The method may be generalized to the community level because the relationship between chitobiase activity liberated into seawater after moult and individual body size was found to be common to three calanoid and one harpacticoid copepod species. This relationship. and the rate of decay of chitobiase in the water column, can be used to estimate the community-level BPR and size-class specific stage durations. Estimates of stage duration based on the turnover rate of chitobiase in the water column were in good agreement (within 5-15%) with both conventional incubation techniques and literature-based estimates. The approach was also used to estimate community-level BPR during a two-year time series in the Straight of Georgia (2004 and 2005) and two broad-scale spatial surveys encompassing shelf, slope and open ocean regions in the subarctic NE Pacific during the spring and late summer of 2004. This thesis presents the development and field validation of a novel method of estimating rates of ...
|
|---|