Coastal systems are increasingly impacted by over-enrichment of nutrients, which has cascading effects for ecosystem functioning. Oyster restoration and aquaculture are both hypothesized to mitigate excessive nitrogen (N) loads via benthic denitrification. The degree to which these management activities perform similar functions for removing N, however, has not been extensively examined in New England, a place where nutrient runoff is high and increasing oyster (Crassostrea virginica) restoration and aquaculture activity is taking place. Here, we use a novel in situ methodology to directly measure net N2 and O2 fluxes across the sediment-water interface in a shallow (~1 m) coastal pond in southern Rhode Island. We collected data seasonally during 2013 and 2014 at restored oyster reefs, oyster aquaculture, oyster cultch (shell), and bare sediment. Restored oyster reefs and aquaculture had the highest mean (± SE) denitrification rates, 581.9 (± 164.2) and 346 (± 168.6) μmol N2-N m-2 h-1, respectively, and are among the highest recorded for oyster-dominated environments. Denitrification rates at sites with oyster cultch were 60.9 (± 44.3) μmol N2-N m-2 h-1, which is substantially less than the sites with active oysters but still more than 50% higher than denitrification rates measured in bare sediment (24.4 ± 10.1 μmol N2-N m-2 h-1). The increase in denitrification rates at treatments, however, varied by season and the greatest rates for restored reefs were in the fall. Overall, the greatest aggregate denitrification rates occurred in the fall. Sediment oxygen demand (SOD) followed similar patterns but with greater overall rates in the summer, and displayed a strong linear relationship with denitrification (R2 = 0.9273). Our results demonstrate that habitats associated with live oysters have higher net denitrification rates and that oyster reef restoration and oyster aquaculture may provide similar benefits to the ecosystem in terms of N removal. However, gas fluxes may also be affected where three-dimensional structure is introduced via oyster shell cultch and this appears to be seasonally-dependent. These data will be important for managers as they incorporate oysters into nutrient reduction strategies and consider system-level trade-offs in services provided by oyster reef restoration and aquaculture activities.

There are millions of small-scale fishers worldwide that rely on coral reefs for their livelihood. Yields from many of these coral reef fisheries, however, have been declining. In Indonesia and other coral reefs worldwide, management approaches are dominated by marine protected areas but other options including gear-restrictions may be feasible and more adaptive to local ecological and social conditions. Yet, there is little data on the impacts and selectivity of fishing gears for coral reef fisheries. In this paper, we present results from a case study on the island of Lombok, where we examine the selectivity and overlap in catch composition of the two main fishing gear types: spearguns and handlines. The catch per unit effort (CPUE) was greater in handlines than spearguns, 10.8 and 9.97 kg trip^-1, respectively. The two gears targeted different fish communities with little overlap in dominant species, suggesting a partitioning of resources; handlines targeted piscivores, whereas spearguns targeted mostly herbivores. Mean trophic level was 3.6 for the handline catch and 2.8 for spearguns, where it was inversely related to CPUE. Spearguns captured more species overall and the number of species increased as the CPUE increased. Length parameters of maturity indicated that neither gear showed signs of (growth) overfishing and fishing grounds dominated by speargun fishers had catches associated with younger ages at first maturity than handlines. Our findings provide local baseline data on the potential utility of gear restrictions as a management tool. Specifically, managers could monitor reefs and reduce handlines when piscivorous fishes are low and on spearguns when species diversity is low or algal abundance is high. Should it become more desirable to implement ecosystem approaches to management that are adaptive to changing ecological and social conditions, these indicators may be used as starting points along with local management preferences of fishers.