Managing Baltic Sea fisheries under contrasting production and predation regimes: ecosystem model analyses

Based on an earlier published ecosystem model, we have explored possible effects of different management scenarios for the Baltic Sea. The scenarios include an oligotrophication of the system, a drastic increase in the number of seals, and changes in the fishery management. From these simulations we conclude that fisheries, seals, and eutrophication all have strong and interacting impacts on the ecosystem. These interactions call for integrated management. The modeling highlights the potential for conflicts among management mandates such as flourishing fisheries, rebuilt seal populations, and substantially reduced eutrophication. The results also suggest that fisheries management reference points have to be adjusted in response to changes in the presence of natural predators or ecosystem productivity.     

Fly ash and lime-stabilized biosolid mixtures in mine spoil reclamation: simulated weathering

The use of large quantities of neutral coal fly ash (NFA) may be facilitated by co-application with a lime-stabilized biosolid (LSB) for the reclamation of acid mine spoil (AMS). Although NFA may not aid in the mitigation of acid drainage, questions concerning the leachability and mineralogy of native and NFA- and LSB-born metals must be addressed. In this study, the potential long-term influence of LSB and NFA on AMS leachate chemistry and trace element mineralogy was evaluated using laboratory weathering and selective dissolution techniques. The application of LSB at a rate sufficient to neutralize the potential acidity of the AMS increased leachate pH from approximately 3 to 7.5 for the duration of the study. Fly ash rates (1X, 1.5X, and 2X LSB rate) did not affect leachate pH. The dominant electrolytes in all leachates were Ca and SO4, the concentrations of which were mirrored by solution electrical conductivity (EC). Leachate concentrations of Al, Fe, Mn, K, Cu, Ni, and Zn were significantly reduced by LSB application, whereas concentrations of Ca, SO4, Mg, Cl, F, B, and P were increased. Nitrate concentrations were not affected by LSB. With the exception of leachate B, which increased with increasing NFA rate and was regenerated during the weathering study, NFA did not affect leachate composition. Sequential selective dissolution indicated a transformation of Co, Cr, Cu, Ni, Pb, and Zn into less labile mineral pools with weathering. The results of these evaluations suggest that the application of NFA during AMS reclamation would have little effect on leachate chemistry or the mineralogy of trace elements. Thus, the high-volume application of NFA to AMS during reclamation may offer an additional opportunity for the use of this combustion by-product.     

Effect of pH on surface characteristics of switchgrass-derived biochars produced by fast pyrolysis

Surface properties of switchgrass-derived biochars produced at fast pyrolysis temperatures of 450, 600 and 800 °C were characterized at different solution pHs in order to determine the structural and chemical changes of artificially-weathered biochars when incorporated into soil. As biochars were acidified from pH 7 to 3, crystalline minerals dissolved slowly releasing nutrients; however, residual minerals were still detected in biochars produced at higher pyrolysis temperatures after pH treatment. Moreover, the amount of exchangeable bases and other inorganic compounds released from the biochars increased when pH decreased. As minerals dissolved from the biochars, total surface area and pore volume were found to increase. Surface functional groups and water vapor adsorption capacity at 0.8 P/P_o also increased, whereas the potential CEC of biochars decreased due to the replacement of exchangeable sites by hydrogen ion. Therefore, during the aging process, it is predicted that soil-incorporated biochars will slowly release nutrients with changes in surface functionality and porosity, which are expected to enhance water holding capacity of soil and provide a beneficial habitat for microbial colonization.     

Use of pelagic prey subsidies by demersal predators in rocky reefs: insight from movement patterns of lingcod

Allochthonous subsidies of energy and nutrients can affect community structure in patchy marine habitats, including rocky reefs, and their ecological consequences may depend on the mechanism of energy transfer. Lingcod (Ophiodon elongatus) are demersal predators that trophically link nearshore rocky reefs with offshore pelagic habitats through consumption of pelagic fishes. We quantified lingcod habitat use and movement patterns to make inferences about the temporal and spatial conditions under which lingcod may acquire pelagic prey. Lingcod maintained small home ranges (21,272 ± 13,630 m²) within a rocky reef in the San Juan Archipelago, Washington; eight of nine individuals used rocky habitat exclusively. Depths occupied by lingcod (0–50 m) coincided with pelagic fish distribution on the rocky reef; however, diel patterns in lingcod activity varied inversely with occurrence of pelagic fishes on the reef. Our findings suggest that the pelagic subsidy to lingcod is not strongly mediated through directed off-reef foraging by lingcod.     

Spatial and seasonal variation in δ15N and δ13C values in a mesopredator shark, Squalus suckleyi, revealed through multitissue analyses

We used variance decomposition to explore the importance of body size, sex, location, and sampling period as predictors of intrapopulation variation in δ¹⁵N and δ¹³C values in spiny dogfish Squalus suckleyi from the Puget Sound–Strait of Georgia basin. Isotopes in two tissues with long (dorsal white muscle) and short (liver) isotopic turnover rates (~1 year and ~3–4 months, respectively) were sampled to evaluate whether the relative importance of each variable differed depending on the time span over which diet information was integrated. Significant spatial variation was observed in both muscle and liver isotopic composition, whereby location uniquely explained 25 and 17 % of the total variance, respectively. The remaining variables explained considerably less variation in both tissue types. Furthermore, evidence of seasonal isotopic shifts in δ¹⁵N and δ¹³C values was apparent, but differed widely in direction and magnitude among groups. These findings suggest that members of spiny dogfish schools may share a common feeding history, possibly by spending extended time periods (weeks to months) foraging in a spatially fixed region. Another explanation is that individuals may move and feed in aggregations that exist for extended periods. These complex group-level patterns suggest that even for large-bodied, motile predators such as sharks, population-level diet estimates derived from averaging isotope ratios of individuals collected from only a few locations may poorly reflect the true population mean.