Potential role of predators on carbon dynamics of marine ecosystems as assessed by a Bayesian belief network.

While the effects of climate change on top predators are well documented, the role of predation on ecosystem level carbon production is poorly developed, despite it being a logical consequence of trophic dynamics. Trophic cascade effects have shown predator mediated changes in primary production, but we predict that predators should lower the overall biomass capacity of any system with top down control. Through a simple Bayesian belief network model of a typical marine foodweb, we show that predator removal, as is common through activities such as fishing and shark finning, results in higher biomasses of lower trophic level fish and zooplankton, resulting in higher net carbon production by the system. In situations common throughout much of the ocean, where activities such as shark finning and over fishing reduce the highest tropic levels, the probability of net carbon production increasing in the model was ~ 60%, and unlike previous studies on simple food chains, trophic cascade effects were not present. While the results are preliminary, and sources of uncertainty in data and models are acknowledged, such results provide even more strength to the argument to protect open sea fish stocks, and particularly large predators such as sharks, cetaceans and game fish

An integrated evaluation of potential management processes on marine reserves in continental Ecuador based on a Bayesian belief network model

Evaluating potential effects of conservation and management actions in marine reserves requires an understanding not only of the biological processes in the reserve, and between the reserve and the surrounding ocean, but also of the effects of the wildlife on the wider political and economic processes. Such evaluations are made considerably more difficult in the absence of good ecological data from within reserves or consistent data between reserves and the wider marine environment, as is the case in much of mainland Ecuador. We present an approach to evaluate the effects of a wide range of possible management processes on the marine ecology of the Machalilla National Park, as well as that of the surrounding marine environments (including recently established reserves) and related socio-economic pressures. The approach is based on Bayesian belief networks, and as such can be used in the presence of sparse data from multiple and disparate sources. We show that currently there are no observable benefits of marine reserves to reef and fish community structure, and that high value (normally predatory) fish, which are sought by fishers and shark finners are frequently absent from reef systems. We demonstrate that there is broad similarity in ecological communities between most shallow marine systems, in or out of marine reserves, and predict there can be a strong effect from actions outside the reserve on what is present within it. We also show that establishing a stronger link between (responsible) ecotourism and the marine environment could reduce the need for income in other more destructive areas, such as fishing and particularly shark finning, and discuss ways that high value, low impact eco-tourism could be introduced