No abstract

Marine benthic habitats are modified by a number of human-related disturbances. When these disturbances occur at large scales over areas of high environmental variability, it is difficult to assess impacts using metrics such as species richness or individual species distributions because of varying species-specific responses to environmental drivers (e.g., exposure, sediment, temperature). Impact assessment can also be problematic when assessed at broad spatial scales because of regional heterogeneity of species pools. Even when effects on individual species can be detected, it is difficult to upscale from individual species to ecosystem scale effects. Here, we use a functional group approach to assess broad scale patterns in ecological processes with respect to fishing and environmental drivers. We used data from field surveys of benthic communities from two large, widely separated areas in New Zealand's EEZ (Chatham Rise and Challenger Plateau). We assigned 828 taxonomic units (most identified to species) into functional groups related to important ecosystem processes and likely sensitivity to, and recovery from, fishing disturbance to the seafloor. These included: opportunistic early colonists; substrate stabilisers (e.g., tube mat formers); substrate destabilisers; shell hash-creating species; emergent epifauna; burrowers; and predators and scavengers. Effects of fishing disturbance on benthic functional composition were observed, even at this broad spatial scale. Responses varied between functional groups, with some being tolerant of fishing impacts and others showing rapid declines with minimal fishing effort. The use of a functional group approach facilitates assessment of impacts across regions and species, allowing for improved generalisations of impacts to inform management and decision making.

Identifying the effects of stressors before they impact ecosystem functioning can be challenging in dynamic, heterogeneous ‘real-world’ ecosystems. In aquatic systems, for example, reductions in water clarity can limit the light available for photosynthesis, with knock-on consequences for secondary consumers, though in naturally turbid wave-swept estuaries, detecting the effects of elevated turbidity can be difficult. The objective of this study was to investigate the effects of shading on ecosystem functions mediated by sandflat primary producers (microphytobenthos) and deep-dwelling surface-feeding macrofauna (Macomona liliana; Bivalvia, Veneroida, Tellinidae). Shade cloths (which reduced incident light intensity by ~80%) were deployed on an exposed, intertidal sandflat to experimentally stress the microphytobenthic community associated with the sediment surface. After 13 weeks, sediment properties, macrofauna and fluxes of oxygen and inorganic nutrients across the sediment-water interface were measured. A multivariate metric of ecosystem function (MF) was generated by combining flux-based response variables, and distance-based linear models were used to determine shifts in the drivers of ecosystem function between non-shaded and shaded plots. No significant differences in MF or in the constituent ecosystem function variables were detected between the shaded and non-shaded plots. However, shading reduced the total explained variation in MF (from 64% in non-shaded plots to 15% in shaded plots) and affected the relative influence of M. liliana and other explanatory variables on MF. This suggests that although shade stress may shift the drivers of ecosystem functioning (consistent with earlier investigations of shading effects on sandflat interaction networks), ecosystem functions appear to have a degree of resilience to those changes.

Funding and priorities for ocean research are not separate from the underlying sociological, economic, and political landscapes that determine values attributed to ecological systems. Here we present a variation on science prioritization exercises, focussing on inter-disciplinary research questions with the objective of shifting broad scale management practices to better address cumulative impacts and multiple users. Marine scientists in New Zealand from a broad range of scientific and social-scientific backgrounds ranked 48 statements of research priorities. At a follow up workshop, participants discussed five over-arching themes based on survey results. These themes were used to develop mechanisms to increase the relevance and efficiency of scientific research while acknowledging socioeconomic and political drivers of research agendas in New Zealand's ocean ecosystems. Overarching messages included the need to: (1) determine the conditions under which "surprises" (sudden and substantive undesirable changes) are likely to occur and the socio-ecological implications of such changes; (2) develop methodologies to reveal the complex and cumulative effects of change in marine systems, and their implications for resource use, stewardship, and restoration; (3) assess potential solutions to management issues that balance long-term and short-term benefits and encompass societal engagement in decision-making; (4) establish effective and appropriately resourced institutional networks to foster collaborative, solution-focused marine science; and (5) establish cross-disciplinary dialogues to translate diverse scientific and social-scientific knowledge into innovative regulatory, social, and economic practice. In the face of multiple uses and cumulative stressors, ocean management frameworks must be adapted to build a collaborative framework across science, governance, and society that can help stakeholders navigate uncertainties and socio-ecological surprises.