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Abstract Strengthening community engagement in stewardship can help to improve management of coastal and freshwater environments (blue spaces). Research suggests that recreational users of natural areas may be more willing to engage in stewardship. However, little research at a population scale has examine how recreation experiences shape psychological ingredients for stewardship. We surveyed 3271 residents of South East Queensland, Australia and quantified willingness to engage in blue space stewardship. We then quantified frequency of different types of blue space recreation, perceptions about threats to blue spaces (threat appraisal) and protective actions (coping appraisal), and satisfaction with blue spaces. We then examined pathways from recreation to stewardship intentions using mediation analysis. Results show that many types of recreation were associated with stewardship intentions. Specifically, higher frequency of social activities and nature‐appreciation activities were associated with greater intentions for individual stewardship (e.g. picking up litter, reducing use of household chemicals). Higher frequency of social activities, nature appreciation, exercise and fishing/boating was associated with stronger intentions for collective stewardship (e.g. attending a public meeting or riparian management event) Mediation analysis showed that most forms of recreation did not influence perceptions about severity of threats to blue spaces. Rather, the relationships between recreation and stewardship were mediated by greater place satisfaction, perceived vulnerability to blue space degradation, and feeling more able to contribute to waterway protection (efficacy). These findings indicate that many types of recreation (not just nature appreciation activities) can be a foundation for engaging in nature stewardship, and reinforce the importance of building efficacy when promoting stewardship. The finding that both place satisfaction and perceived vulnerability to environmental degradation suggests that there may be an optimal motivational window for stewardship: people need to connect a place with positive experiences, and have some recognition of a potential threat, but where the potential threat has not yet eroded the natural values of a place. Read the free Plain Language Summary for this article on the Journal blog.

Point- and non-point source nutrients are likely to have different ecological impacts in receiving waters, due to differences in the concentration and proportions of nutrient fractions. However, the direct comparison of their ecological impacts in receiving waters has barely been quantified. We undertook algal bioassays with algal communities from river sites and showed that there was a photosynthetic yield (Fv/Fm) response to nutrient enrichment when river nutrient concentrations were relatively low, but not at higher nutrient concentrations. To combat this variability in the photosynthetic state of algae, we developed a standardized algal bioassay (3-day), using a cultured species of algae which was starved of nitrogen, to compare the photosynthetic response to three nitrogen sources: treated wastewater, aquaculture farm discharges, and soil erosion-derived nutrient sources. This study showed that the nutrient parameter that had the highest correlation with algal photosynthetic response was total dissolved nitrogen (TDN), i.e., the sum of dissolved inorganic and organic nitrogen, rather than dissolved inorganic nitrogen alone. This was true across all three nutrient sources (R2 = 0.58–0.78). Additionally, the same concentrations of TDN from soil erosion-derived and aquaculture samples resulted in a significantly higher algal photosynthetic response, compared to the treated wastewater. This indicates that TDN from soils and aquaculture farms was significantly more bioavailable to the cultured algae than treated wastewater. When a range of parameters were correlated with algal responses, organic and inorganic nutrients, and organic carbon were the parameters that had the highest explanatory power for soil erosion-derived and aquaculture samples (R2 = 0.75–0.87). The importance of organic compounds in these equations points to the potential of microbial transformation of organic nutrients into more bioavailable forms during the 3-day bioassay. This highlights the need to understand the relationship between algal and microbial communities in natural systems for nutrient source impact assessment. This study provides an improved understanding and metrics for comparing the algal growth response to different nutrient sources.

Subtropical systems experience occasional severe floods, dramatically altering the phytoplankton community structure, in response to changes in salinity, nutrients, and light. This study examined the effects of a 1:100 year summer flood on the phytoplankton community in an Australian subtropical bay – Moreton Bay – over 48 weeks, from January to December 2011. Immediately after maximum flood levels were reached on the rivers flowing into the bay, the lowest salinity, and highest turbidity values, in more than a decade, were measured in the Bay and the areal extent of the flood-related parameters was also far greater than previous flood events. Changes in these parameters together with changes in Colored Dissolved Organic Matter (CDOM) and sediment concentrations significantly reduced the light availability within the water column. Despite the reduced light availability, the phytoplankton community responded rapidly (1–2 weeks) to the nutrients from flood inputs, as measured using pigment concentrations and cell counts and observed in ocean color satellite imagery. Initially, the phytoplankton community was totally dominated by micro-phytoplankton, particularly diatoms; however, in the subsequent weeks (up to 48-weeks post flood) the community changed to one of nano- and pico-plankton in all areas of the Bay not usually affected by river flow. This trend is consistent with many other studies that show the ability of micro-phytoplankton to respond rapidly to increased nutrient availability, stimulating their growth rates. The results of this study suggest that one-off extreme floods have immediate, but short-lived effects, on phytoplankton species composition and biomass as a result of the interacting and dynamic effects of changes in nutrient and light availability.