Co-Producing Narratives and Indicators as Catalysts for Adaptive Governance of a Common-Pool Resource within a Protected Area.

The theory and practice of adaptive management and adaptive governance have been widely studied in the complex social contexts that mediate how humans interact with ecosystems. Adaptive governance is thought to enable adaptive management in such contexts. In this study, we examine four often-used principles of adaptive governance (polycentric institutions, collaboration, social learning and complexity thinking) to develop a framework for reflecting on adaptive governance of a social-ecological system-the Knysna Estuary in South Africa. This estuary is a priority for biodiversity conservation, as well as a common-pool resource central to livelihoods. We used the framework to structure dialogue on the extent to which the four principles of adaptive governance were being applied in the management of the Knysna Estuary. The dialogue included diverse stakeholders, from those who have the power to influence adaptive management to those most dependent on the resource for their livelihoods. Based on a combination of theory and current reality we then identified eight indicators that could be used to guide a transition towards improved adaptive governance of the estuary. These indicators were assessed and supported by most stakeholders. The main contributions of our research are (a) a process for combining theory and stakeholder dialogue to reflect on adaptive governance of a social-ecological system; (b) a set of indicators or conditions that emerged from our participatory process that can be used for reflexive monitoring and adaptation of adaptive governance of Knysna Estuary; and (c) a real-world example of seeking complementary links between adaptive governance and adaptive management to promote effective management of complex social-ecological systems.

Conservation value of Codium tenue habitat for the endangered Knysna seahorse Hippocampus capensis.

We investigated the density and size structure of the endangered Knysna seahorse Hippocampus capensis in the macroalga Codium tenue at three sites in a residential marina estate in the Knysna Estuary, South Africa, over an 18 month period from March 2017 to August 2018. Seahorses were present in C. tenue throughout the year. Average (± SE) densities of 0.33 (± 0.03) and 0.23 (± 0.03) seahorses per kg of C. tenue were found for 2017 and 2018 respectively. Density did not vary across sites but varied significantly across months with a decreasing trend from summer to spring. The average (± SE) adult seahorse height was 75.16 mm (± 0.63 mm) and 69.09 mm (± 0.64 mm) and mass was 2.05 g (± 0.04 g) and 1.65 g (± 0.04 g) for males and females, respectively, and an even sex ratio was observed throughout the sampling period. Height varied across months, with significantly smaller seahorses found in June and August of 2017. Tail length was highly correlated with height and therefore can serve as a potential proxy for determining the height of H. capensis. This study showed that C. tenue is consistently utilised by Knysna seahorse and should therefore be considered an important habitat to protect and facilitate the ongoing conservation of this endangered seahorse species.

Monthly population density and structure patterns of an endangered seahorse Hippocampus capensis: a comparison between natural and artificial habitats.

This study investigated aspects of the population ecology of the endangered Knysna seahorse Hippocampus capensis within different habitat types. High densities of H. capensis were found within artificial Reno mattress habitat, within the Knysna Estuary, South Africa. Monthly surveys at three sites were conducted from October 2015 to August 2016 to compare population densities of H. capensis in this artificial habitat with natural eel grass Zostera capensis habitat. Hippocampus capensis densities varied significantly across all sites and highest population densities were consistently observed within the Reno mattress habitat. Hippocampus capensis were also found to be significantly larger within the Reno mattress habitat and pooled data showed that males were significantly larger than females. The overall sex ratio for all three sites was female biased, although this varied across seasons at two sites. The findings suggest that artificial Reno mattresses provide novel habitat for this endangered species and consideration should be given to the usefulness of these structures in future conservation actions.

Interspecific abundance-occupancy relations along estuarine gradients.

Do interspecific abundance-occupancy (A-O) relationships vary systematically along environmental gradients? A-O relationships of macrobenthic assemblages of seagrass and adjacent bare-sediment were compared at series of sites along two types of estuarine gradient; the longitudinal one of the main axial channel, and a transverse one from that channel into progressively smaller channels and creeks enclosed within fringing saltmarsh. Three general features emerged: A-O regression slopes were remarkably uniform across all the disparate assemblages and sites (1.04 ± 0.08); values of R2 were very high (≈0.96); and where small but significant differences between sites occurred, they were associated with the stronger gradients (i.e. those with the larger differentials in abundance and smaller compositional similarities). In two such cases, slope values were correlated with position along the gradient (although only at the margin of statistical significance). Variation in A-O relationships along estuarine gradients does clearly occur, but their constancy leaves the stronger impression.

Where ecologically 'tis better to go brown than green: enhanced seagrass macrobenthic biodiversity within the canals of a brownfield coastal marina.

At the start of the 21st century, a coastal residential-estate marina was developed on a previously degraded and polluted brownfield island site within Knysna estuarine bay, Garden Route National Park, South Africa, including the creation of 25 ha of new flow-through tidal canals. Canals near the larger entrance to this system now support permanently submerged beds of seagrass, which in turn support abundant macrobenthic invertebrates. In comparison with equivalent seagrass-associated assemblages present in natural channels around the island, those in the artificial marina canals were similarly structured and dominated by the same species, but the marina assemblages were significantly more species-rich (1.4 x on average) and were more abundant. Indeed, this area of marina supports the richest seagrass-associated macrofaunal biodiversity yet recorded from South Africa. The canals created de novo therefore now form a valuable addition to the bay's marine habitat, in marked contrast to the generality that marinas developed on greenfield sites represent a net reduction in intertidal and shallow marine area and associated seagrass-associated benthos. If located and constructed appropriately, brownfield marina development and conservation of coastal marine biodiversity clearly need not be antithetical, and brownfield sites may provide opportunity for the location and management of 'artificial marine micro-reserves' or for the action of 'other effective area-based conservation measures' for soft-sediment faunas.

Local patchiness of macrobenthic faunal abundance displays homogeneity across the disparate seagrass systems of an estuarine bay.

Spatial variation in the degree of local patchiness of macrobenthic assemblage abundance was assessed across the 16 km2 warm-temperate Knysna estuarine bay (South Africa) where the seagrass Zostera (Zosterella) capensis grows under a broad spectrum of environmental conditions and supports invertebrate assemblages at a wide range of local density (<2000->320000 ind. m-2). Macrobenthic assemblage abundance at all 27 representative sites examined displayed low-level but highly-significant spatial patchiness (mean Lloyd's index, IP = 1.148). Except at high tidal levels, however, the magnitude of this local patchiness did not vary statistically across the system (CV 4.3%) regardless of assemblage abundance, location or species composition. Patchinesses well within ±1 standard deviation of Knysna's value also characterise an equivalent Z. (Zosterella) capricorni assemblage in subtropical Queensland (IP 1.169) and another, Z. (Zosterella) noltei, assemblage in cool-temperate England (IP 1.135), suggesting that at local scales intertidal dwarf-eelgrass macrobenthic abundance displays a characteristic level of patchiness.

Biodiversity differentials between the numerically-dominant macrobenthos of seagrass and adjacent unvegetated sediment in the absence of sandflat bioturbation.

Species composition, abundance and biodiversity of the South African estuarine invertebrate fauna are known to show marked differentials between seagrass beds and adjacent unvegetated sands in enclosed estuarine/marine bays. Such differentials were investigated at four disparate localities in a bay lacking the callianassid bioturbation of other local sites. Here there were no such marked or consistent differences: <50% of differentials were statistically significant, with seagrass showing the lower, not higher, level in half of those. Overall, faunal abundance was lower in seagrass in the ratio of 0.64 : 1, whilst species density was higher but only by 1.13 to 1. Seagrass assemblages at a given locality were more similar to those of the adjacent bare sand than they were to seagrass assemblages at other localities, and likewise in respect of those in the bare sand. This suggests that marked differentials, where they occur, may result not from any supposed favourability of seagrass as a habitat but from the operation of processes within the unvegetated-sediment compartment of the system.