Assemblages of macroalgae are believe to be among the most productive ecosystems in the world, yet difficulties in obtaining direct estimates of biomass and primary production have led to few macroalgal data sets from which the consequences of long-term change can be assessed. We evaluated the validity of using two easily measured population variables (frond density and plant density) to estimate the more difficult to measure variables of standing crop and net primary production (NPP) in the giant kelp Macrocystis pyrifera off southern California. Standing crop was much more strongly correlated to frond density than to plant density. Frond density data collected in summer were particularly useful for estimating annual NPP, explaining nearly 80% of the variation in the NPP from year to year. Data on frond densities also provided a relatively good estimate of seasonal NPP for the season that the data were collected. In contrast, estimates of seasonal and annual NPP derived from plant density data were less reliable. These results indicate that data on frond density collected at the proper time of year can make assessments of NPP by giant kelp more tractable. They also suggest that other easily measured variables that are strongly correlated with standing crop, such as surface canopy area, might serve as similarly useful proxies of NPP.

Marine spatial planning (MSP), whereby areas of the ocean are zoned for different uses, has great potential to reduce or eliminate conflicts between competing management goals, but only if strategically applied. The recent literature overwhelmingly agrees that including stakeholders in these planning processes is critical to success; but, given the countless alternative ways even simple spatial regulations can be configured, how likely is it that a stakeholder-driven process will generate plans that deliver on the promise of MSP? Here, we use a spatially explicit, dynamic bioeconomic model to show that stakeholder-generated plans are doomed to fail in the absence of strong scientific guidance. While strategically placed spatial regulations can improve outcomes remarkably, the vast majority of possible plans fail to achieve this potential. Surprisingly, existing scientific rules of thumb do little to improve outcomes. Here, we develop an alternative approach in which models are used to identify efficient plans, which are then modified by stakeholders. Even if stakeholders alter these initial proposals considerably, results hugely outperform plans guided by scientific rules of thumb. Our results underscore the importance of spatially explicit dynamic models for the management of marine resources and illustrate how such models can be harmoniously integrated into a stakeholder-driven MSP process.

Ecological communities can undergo sudden and dramatic shifts between alternative persistent community states. Both ecological prediction and natural resource management rely on understanding the mechanisms that trigger such shifts and maintain each state. Differentiating between potential mechanisms is difficult, however, because shifts are often recognized only in hindsight and many occur on such large spatial scales that manipulative experiments to test their causes are difficult or impossible. Here we use an approach that focuses first on identifying changes in environmental factors that could have triggered a given state change, and second on examining whether these changes were sustained (and thus potentially maintained the new state) or transitory (explaining the shift but not its persistence). We use this approach to evaluate a community shift in which a benthic marine species of filter feeding sea cucumber (Pachythyone rubra) suddenly came to dominate subtidal rocky reefs that had previously supported high abundances of macroalgae, persisted for more than a decade, then abruptly declined. We found that a sustained period without large wave events coincided with the shift to sea cucumber dominance, but that the sea cucumbers persisted even after the end of this low wave period, indicating that different mechanisms maintained the new community. Additionally, the period of sea cucumber dominance occurred when their predators were rare, and increases in the abundance of these predators coincided with the end of sea cucumber dominance. These results underscore the complex nature of regime shifts and illustrate that focusing separately on the causes and maintenance of state change can be a productive first step for analyzing these shifts in a range of systems.

Sarah Lester et al. argue that sustainable seafood certification programs are missing a critical opportunity by failing to provide credit for marine protected areas. Fixing this oversight will improve the leverage of certification programs to drive sustainable fishing, with significant benefits to fish and fisheries.

Oceans currently face a variety of threats, requiring ecosystem-based approaches to management such as networks of marine protected areas (MPAs). We evaluated changes in fish biomass on temperate rocky reefs over the decade following implementation of a network of MPAs in the northern Channel Islands, California. We found that the biomass of targeted (i.e. fished) species has increased consistently inside all MPAs in the network, with an effect of geography on the strength of the response. More interesting, biomass of targeted fish species also increased outside MPAs, although only 27% as rapidly as in the protected areas, indicating that redistribution of fishing effort has not severely affected unprotected populations. Whether the increase outside of MPAs is due to changes in fishing pressure, fisheries management actions, adult spillover, favorable environmental conditions, or a combination of all four remains unknown. We evaluated methods of controlling for biogeographic or environmental variation across networks of protected areas and found similar performance of models incorporating empirical sea surface temperature versus a simple geographic blocking term based on assemblage structure. The patterns observed are promising indicators of the success of this network, but more work is needed to understand how ecological and physical contexts affect MPA performance.

Sarah Lester et al. argue that sustainable seafood certification programs are missing a critical opportunity by failing to provide credit for marine protected areas. Fixing this oversight will improve the leverage of certification programs to drive sustainable fishing, with significant benefits to fish and fisheries.

The transformation of coral reefs has profound implications for millions of people. However, the interactive effects of changing reefs and fishing remain poorly resolved. We combine underwater surveys (271 000 fishes), catch data (18 000 fishes), and household surveys (351 households) to evaluate how reef fishes and fishers in Moorea, French Polynesia responded to a landscape-scale loss of coral caused by sequential disturbances (a crown-of-thorns sea star outbreak followed by a category 4 cyclone). Although local communities were aware of the disturbances, less than 20% of households reported altering what fishes they caught or ate. This contrasts with substantial changes in the taxonomic composition in the catch data that mirrored changes in fish communities observed on the reef. Our findings highlight that resource users and scientists may have very different interpretations of what constitutes 'change' in these highly dynamic social-ecological systems, with broad implications for successful co-management of coral reef fisheries.