Environmental Engineering Reference
In-Depth Information
Cascade effect of changes in primary and secondary production on
future biological production
Brander (2010) has reported that changes in primary and secondary
production will obviously have a major effect on fi sheries production, but
the complexity of the trophic systems leading from primary production
to fi sh makes it diffi cult to establish reliable predictive relationships.
Although global aggregated marine primary production is not expected
to change substantially over the next 4 or 5 decades, there is a stronger
basis for predicting changes in production at regional level and also good
observational evidence, particularly for the North Pacific and North
Atlantic (Jennings and Brander 2010). In both cases changes in production
are driven mainly by regime-scale and event-scale (e.g., El Niño) changes
(Brander 2010).
In the Arctic Ocean, the reduction in ice cover will allow light to
penetrate in new areas and therefore increase the productive area, but the
retreat of the highly productive marginal sea-ice zone will disrupt the
existing food web (Santhi Pechsiri et al. 2010). In the “new” ice-free areas of
the Arctic Ocean production is likely to be limited by nutrient supply due
to the increased freshwater input from Arctic rivers (Prowse et al. 2006).
Brander (2010) highlighted that this will increase vertical stratifi cation
and hence reduce the vertical fl ux of nutrients. The riverine input is also
nutrient poor.
Qualitative changes in production may have major impacts on food
chains leading to fi sh regardless of changes in the absolute level of primary
production (Jarre et al. 2006). In this sense, Atkinson et al. (2004) presented
results including the observed switch from krill to salps as the major
nektonic species in parts of the Antarctic, while Daskalov (2002) did with
the ascendance of gelatinous species to a dominant position in areas such
as the Black Sea. In the former case climate change was probably a major
factor, but in the latter it was not (Brander 2010).
Regional consequences of changes in primary production
A large amount of information is available on this topic, and several of the
most remarkable examples are as follows:
Tropical Pacifi c
Tuna species fi sheries (e.g., skipjack
Katsuwonus pelamis
, yellowfi n
Thunnus
albacares
, albacore
Thunnus alalunga
) are the most important within the area,
representing more than 3.5 million tons/year (Bigelow and Maunder 2007).
The catches and distribution of these species are governed by variability
in primary production and location of suitable habitat for spawning and
