Environmental Engineering Reference
In-Depth Information
allowed a deeper mixing and a transfer of more nutrients to the surface. This
climatic forcing modifi ed the carrying capacity of the central North Pacifi c
gyre, contributing to an increase in the abundance of fi shes such as the
Alaskan salmon and cod, and a decrease in the abundance of shrimps.
It has been diffi cult to demonstrate shifts between alternative stable
dynamic regimes in the real world (Scheffer et al. 2001). To demonstrate that
an ecosystem regime shift may have actually happened stepwise changes
should be detected (1) across different trophic levels, (2) at the level of the
community structure, (3) for key species, (4) in attributes of ecosystems
such as diversity, and (5) one should expect that ecosystem changes would
refl ect hydro-climatic variability.
Effects of Climate Change on Marine Ecosystems
The functioning of marine ecosystems is supported by the fl ow of energy
going from primary producers to intermediate consumers, top predators
(including humans) and pathogens, and then back through the process
of decomposition and generation of debris (Moore and de Ruiter 2012).
So, it is clearly understood that marine communities are biological
networks where the success of species is directly or indirectly linked
through various biological interactions (e.g., predator-prey relationships,
competition, facilitation, mutualism) to the performance of other species
within the community (Werner and Peacor 2003). Within this theoretical
framework, Doney et al. (2009) emphasized that the aggregate effect of
these interactions constitutes ecosystem function (e.g., nutrient cycling,
primary and secondary productivity), through which ocean and coastal
ecosystems provide the wealth of free natural benefi ts that society depends
upon, such as fi sheries and aquaculture production, water purifi cation,
shoreline protection and recreation.
Climate change pressures are having profound and diverse
consequences for marine ecosystems. Rising atmospheric CO
2
is one of
the most critical problems because its effects are globally pervasive and
irreversible on ecological timescales (Raven et al. 2005). The primary direct
consequences are increasing ocean temperatures (IPCC 2007c) and acidity
(Doney et al. 2009). Climbing temperatures create a host of additional
changes, such as rising sea level, increased ocean stratifi cation, decreased
sea-ice extent, and altered patterns of ocean circulation, precipitation, and
freshwater input. In addition, both warming and altered ocean circulation
act to reduce subsurface oxygen (O
2
) concentrations (Keeling et al. 2010).
In recent decades, the rates of change have been rapid and may exceed
the current and potential future tolerances of many organisms to adapt.
Further, the rates of physical and chemical change in marine ecosystems will
