Evaluating impacts of intensive shellfish aquaculture on a semi-closed marine ecosystem

- Ecopath model was used to evaluate the role of intensive shellfish aquaculture in an ecosystem.
- Culture shellfish led to shifts of major energy sources of Jiaozhou Bay ecosystem from detritus to phytoplankton.
- Intensive shellfish aquaculture improve the transfer efficiency of the ecosystem and simplify the food web.
- Consumption of phytoplankton by cultured shellfish consisted of 90% of total phytoplankton consumption.

Shellfish aquaculture production in the world, especially in China, has expanded rapidly in recent years. However, understanding of potential impacts of shellfish aquaculture on the trophic structure of ecosystem remains limited. Using an Ecopath with Ecosim model, we compared various shellfish aquaculture intensity scenarios to evaluate impacts of shellfish aquaculture on a semi-closed marine ecosystem, located in Jiaozhou Bay, China. This study showed that the Jiaozhou Bay ecosystem could be strongly impacted by the shellfish aquaculture as illustrated by the ecosystem indices such as total system throughout (TST), Finn's cycle index (FCI), and System omnivory index (SOI). The existence of shellfish aquaculture program led to shifts of major energy sources of Jiaozhou Bay ecosystem from detritus to phytoplankton. Contribution of phytoplankton to the ecosystem energy flow could drop from 75% to 46% if the current shellfish aquaculture program was removed. Intensive shellfish aquaculture could also improve the transfer efficiency of the ecosystem and simplify the food web. In addition, consumption of phytoplankton by cultured shellfish consisted of 90% of total phytoplankton consumption in this ecosystem, indicating that cultured shellfish could exert strong top-down control on phytoplankton in the Jiaozhou Bay ecosystem. Our results demonstrated that intensive cultured shellfish program shifted Jiaozhou Bay ecosystem from a natural-organism-dominated food web into an aquaculture dominated food web. Given these caveats, cultured shellfish is not only economically efficient, but also ecologically efficient. This study suggests that it is informative and necessary to conduct holistic and integrated ecosystem analyses to improve our understanding of potential impacts of shellfish aquaculture on the ecosystem dynamics.