Application 124771 - Ministry of Fisheries
Application 124771 - Ministry of Fisheries
Application 124771 - Ministry of Fisheries
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
MAY 2012 REPORT NO. 2134 | CAWTHRON INSTITUTE<br />
6<br />
3.2. Water column effects<br />
Effects <strong>of</strong> mussel cultivation on the water column are less well defined than for the<br />
seabed, because water column characteristics are more dynamic and inherently<br />
harder to quantify. The physical presence <strong>of</strong> farms can alter and reduce current<br />
speeds, which affects water residence times and has implications for associated<br />
biological processes. Farm structures can also attenuate short-period waves (Plew et<br />
al. 2005), which can affect inshore ecology, but these issues are not considered<br />
significant at the present scale <strong>of</strong> development in New Zealand. Bivalves and other<br />
associated fauna release dissolved nitrogen (e.g. ammonium) directly into the water<br />
column, which can cause localised enrichment and stimulate phytoplankton growth.<br />
Toxic microalga blooms may lead to ecological or health problems, but there is no<br />
evidence <strong>of</strong> this being exacerbated by mussel farming in New Zealand waters.<br />
Filtration pressure by mussels is sufficient to potentially alter the composition <strong>of</strong> the<br />
phytoplankton and zooplankton/mesoplankton communities through feeding, but the<br />
extent to which this occurs and its ecological consequences are poorly understood.<br />
Despite the recognised knowledge gaps, the fact that no significant water column<br />
related issues have been documented, suggests that effects associated with<br />
traditional inshore farming practices are minor (Keeley et al. 2010).