Ecosystem Grazing

We now know that the Earth’s living components regulate numerous fluxes of energy and matter. In coastal and estuarine ecosystems with dense populations or subsystems of bivalves, these organisms often represent a major functional component that consumes large quantities of primary producers and strongly couples the benthic and water column habitats to each other. In these systems, bivalves graze on phytoplankton in the water column, benthic microflora, “resuspended” benthic algae, detritus, or all of the above. They also can remove some of their potential food competitors, the microzooplankton that also includes their own larvae. Thus the role of the bivalves in moving energy and materials through and within their ecosystems is prominent. When measured at local scales, these rates are usually called ecosystem processes. Ecosystem properties are attributes of the biotic assemblage in terms of the number and types of organisms. The combination of processes, properties, and their maintenance represent ecosystem functioning (Reiss et al. 2009), but to avoid confusion, I agree with Norberg and Comming (2008) and advocate using the term “ecosystem processes.” Important Terms and Concepts Complex systems

Produce unexpected dynamics because of nonlinear interactions among components.

Ecological restoration

The process of assisting in the recovery of damaged ecosystems.

Ecosystem functions

Attributes of an ecosystem that help to keep its component parts running together.

Ecosystem processes

Defined or described in terms of delivery, movement, or loss of energy or materials to an ecosystem.

Ecosystem services

Processes that are beneficial to humans.

Estuarine ecosystems

Coastal bodies of water where seawater meets and mixes with freshwater from land and ground runoff.

Feedback

An output signal that controls the future magnitude of a flow.

Resilience

The amount of disturbance a system can absorb while still remaining within the same state or domain of attraction.