Physical carrying capacity of a potential aquaculture site in the Mediterranean: the case of Sigacik Bay, Turkey.

The aim of the present study was to evaluate physical carrying capacity of a potential cage aquaculture site near a Cittaslow area in the northern part of the Mediterranean (Sigacik Bay, Turkey). Developing tools for timely management of marine aquaculture facilities are important to minimize harmful influences of fish farming. The physical carrying capacity was estimated by mathematical formulations previously developed for the same area, using data of topographical characteristics of the site, production capacities, and leased area information of fish farms in total. Based on the findings of the present study, estimated physical carrying capacity of the potential aquaculture site with a total area of 38.9 ha near the Cittaslow residential area of "Sigacik Bay" was found as 27,694 tons of fish production which is more than 2-fold of the present production level that is around 11,800 tons in the area. Therefore, it might be concluded from a physical point of view that the production level of the present cage farms in Sigacik Bay is below risk levels.

Human exposure to trace elements via farmed and cage aggregated wild Axillary seabream (Pagellus acarne) in a copper alloy cage site in the Northern Aegean Sea.

Axillary seabream (Pagellus acarne) farmed in a copper alloy mesh pen and wild individuals of P. acarne aggregated near the copper-alloy cages presented higher concentrations of trace metals in the liver, skin and gills than in fish muscle tissues in two batches of small and large fish sizes. Elevated mean levels of metals (mg kg-1) in muscle tissues in both small and large fish size groups were observed in the rank order of Zn(3.43) > Fe(3.01) > Cu(0.59) > Mn(0.13) and Fe(3.82) > Zn(3.32) > Cu(0.62) > Mn(0.17) for copper cage-farmed fish, relative to ranked mean levels for Zn(2.64) > Fe(1.95) > Cu(0.25) > Mn(0.09) and Fe(5.79) > Zn(3.58) > Cu(0.58) > Mn(0.28) for the copper cage-aggregated wild fish. Nevertheless, trace metal concentrations in fish harvested from the copper cage or those of the cage-aggregated wild individuals in both size groups were far below maximum levels of seafood safety recommended by USEPA and FAO/WHO. Target hazard quotients, calculated to estimate the non-carcinogenic health risks of metals by consuming these fish, were below "1″ (THQ < 1), indicating that there were no potential health risks for humans when consuming copper-caged fish or wild-caught individuals aggregated around the copper mesh pen, with respect to the limits suggested by US Food and Drug Administration and EU Regulations for Seafood Consumption.

Fundamental predictability in multispecies competition: the influence of large disturbance.

Empirical evidence of chaos, or complex behavior, in ecosystems is scarce, presumably due to high system-level noise and/or the rarity of conditions necessary for complex behavior to arise. An alternative explanation might be that complex behavior is fragile and readily suppressed by disturbances that are common in many ecosystems. Here we investigated the role of disturbance frequency and magnitude on complex behavior and focused on population succession trajectories in a plankton system. Because of its prominence in aquatic ecology, we used hydraulic flushing and nutrient loading as disturbances. Our findings from numerical modeling exercises and laboratory microcosm experiments using natural plankton assemblages indicated that one aspect of complex behavior, divergence of nearby trajectories, was suppressed when the magnitude and periodicity of hydraulic flushing and nutrient loading were large. In other words, complex succession became determinable. Divergence of nearby trajectories was relatively robust, however, because pulses of not less than 85% of the total inflow were required to suppress this behavior. Our numerical findings also revealed that large hydraulic disturbances could introduce to the system another aspect of complex behavior, aperiodic succession.