Kaneohe Bay Sewage Diversion Experiment: Perspectives on Ecosystem Responses to Nutritional Perturbation

Kaneohe Bay, Hawaii, received increasing amounts of sewage from the 1950s through 1977. Most sewage was diverted from the bay in 1977 and early 1978. This investigation, begun in January 1976 and continued through August 1979, described the bay over that period, with particular reference to the responses of the ecosystem to sewage diversion. The sewage was a nutritional subsidy. All of the inorganic nitrogen and most of the inorganic phosphorus introduced into the ecosystem were taken up biologically before being advected from the bay. The major uptake was by phytoplankton, and the internal water-column cycle between dissolved nutrients, phytoplankton, zooplankton, microheterotrophs, and detritus supported a rate of productivity far exceeding the rate of nutrient loading. These water-column particles were partly washed out of the ecosystem and partly sedimented and became available to the benthos. The primary benthic response to nutrient loading was a large buildup of detritivorous heterotrophic biomass. Cycling of nutrients among heterotrophs, autotrophs, detritus, and inorganic nutrients was important. With sewage diversion, the biomass of both plankton and benthos decreased rapidly. Benthic biological composition has not yet returned to presewage conditions, partly because some key organisms are long-lived and partly because the bay substratum has been perturbed by both the sewage and other human influences

Plankton patchiness and ecosystem stability

Typescript (photocopy)Bibliography: leaves 163-177.Microfiche.xi, 177 leaves, bound ill., maps 29 cmSpatial variability in the controlling rate functions of planktonic ecosystems has been hypothesized to add stability or persistence of species. I have determined the spatial variability in three measures of rate functions in the Kaneohe Bay planktonic ecosystem, one indirect and two direct. 1) The indirect measure, copepod stage frequency distribution, showed spatial variation which was transient. Temporal variation, however, was greater than spatial variation. 2) Copepod production:biomass (P:B) ratios were surprisingly uniform; in only one case out of three was there significant spatial variability, apparently caused by food limitation at one station. 3) Egg production rate was more variable both in space and in time. As with stage frequency distribution, the variability did not occur in a fixed pattern, and temporal variability was greater. Thus spatial heterogeneity of rate functions does exist in Kaneohe Bay but may not be as important to the ecosystem as temporal heterogeneity. To examine the effect on simple ecosystems of mixing between patches, I enclosed parcels of Bay water in 1.3 m^3 tanks and exchanged water daily between two of them. In both experiments the plankton populations underwent drastic shifts in composition, with the copepods starving and being replaced by rotifers. The experimental ecosystems bore little resemblance to the Kaneohe Bay planktonic ecosystem after only two weeks of incubation. Mixing between tanks did not affect either persistence of species or variability in their abundances. It therefore appears that horizontal spatial heterogeneity may not be important to the stability of planktonic ecosystems

Effect of ocean acidification on the nutritional quality of marine phytoplankton for copepod reproduction.

Phytoplankton are the oceans' principal source of polyunsaturated fatty acids that support the growth and reproduction of consumers such as copepods. Previous studies have demonstrated ocean acidification (OA) can change the availability of polyunsaturated fatty acids to consumer diets which may affect consumer reproduction. Two laboratory experiments were conducted to examine the effects of feeding high-pCO2-reared phytoplankton on copepod egg production, hatching success, and naupliar survival. Marine phytoplankton Rhodomonas salina, Skeletonema marinoi, Prorocentrum micans, and Isochrysis galbana were exponentially grown in semi-continuous cultures at present (control) (400 ppm CO2, pH~8.1) and future (1,000 ppm CO2, pH~7.8) conditions and provided to Acartia tonsa copepods over 4 consecutive days as either nitrogen-limited (Exp. I) or nitrogen-depleted (Exp. II) mixed assemblage of phytoplankton. The composition of FAs in the phytoplankton diet was affected by pCO2 concentration and nitrogen deficiency; the ratio of essential fatty acids to total polyunsaturated fatty acids decreased in phytoplankton grown under high pCO2 and the mass of total fatty acids increased under nitrogen depletion. Additionally, total concentrations of essential fatty acids and polyunsaturated fatty acids in the diet mixtures were less under the high-pCO2 compared to the control-pCO2 treatments. Median egg production, hatching success, and naupliar survival were 48-52%, 4-87%, and 9-100% lower, respectively, in females fed high-pCO2 than females fed low-pCO2 phytoplankton, but this decrease in reproductive success was less severe when fed N-depleted, but fatty acid-rich cells. This study demonstrates that the effects of OA on the nutritional quality of phytoplankton (i.e., their cellular fatty acid composition and quota) were modified by the level of nitrogen deficiency and the resulting negative reproductive response of marine primary consumers

Supplement 1. WinBUGS and R code to fit change point and variable selection models.

<h2>File List</h2><blockquote> <p><a href="trend model with changepoints.txt">trend model with changepoints.txt</a>  - WinBUGS model file for trend model with change points<br> <a href="R code to fit trend model with change-points.R">R code to fit trend model with change-points.R</a>  - R script for fitting trend model via R2WinBUGS<br> <a href="varselect model.txt">varselect model.txt</a>  - WinBUGS model file for non-linear variable selection model<br> <a href="R code to fit variable selection model.R">R code to fit variable selection model.R</a>  - R script for fitting variable selection model via R2WinBUGS<br> <a href="CCCP model.txt">CCCP model.txt</a>  - WinBUGS model file for covariate conditioned change point model<br> <a href="R code to fit cccp model.R">R code to fit cccp model.R</a>  - R script for fitting covariate conditioned change point model via R2WinBUGS<br> <a href="multispecies changepoint.txt">multispecies changepoint.txt</a>  - WinBUGS model file for multi-species covariate conditioned change point model<br> <a href="R code to fit multispecies cccp model.R">R code to fit multispecies cccp model.R</a>  - R script for fitting multi-species covariate conditioned change point model via R2WinBUGS<br> <a href="Data.zip">Data.zip</a>  - Data saved as R objects to demonstrate use of R scripts and WinBUGS models</p> <p><br> <a href="All files.zip">Download all files.zip</a> </p> </blockquote><h2>Description</h2><blockquote> <p>The .txt files are WinBUGS model codes for the models described in the paper. These models require the reversible "jump" add-on for WinBUGS (available from WinBUGS development website). The R scripts can be used to generate required data files and run the WinBUGS models from R. Data.zip contains example input data for all models. The R scripts require all files to be in the R working directory and the R2WinBUGS package must be installed.</p> </blockquote

Appendix A. Details of prior distributions used in change point and associated regression models.

Details of prior distributions used in change point and associated regression models