Natural ecological restoration is a cornerstone of modern conservation science and managers need more documented “success stories” to lead the way. In French mediterranean sea, we monitored Posidonia oceanica lower limit using acoustic telemetry and photogrammetry and investigated the descriptors driving its variations, at a national scale and over more than a decade. We showed significant effects of environmental descriptors (region, sea surface temperature and bottom temperature) but also of wastewater treatment plant (WWTP) effluents proxies (size of WWTP, time since conformity, and distance to the closest effluent) on the meadows lower limit progression. This work indicates a possible positive response of P. oceanica meadows to improvements in wastewater treatment and a negative effect of high temperatures. While more data is needed, the example of French wastewater policy should inspire stakeholders and coastal managers in their efforts to limit anthropogenic pressures on vulnerable ecosystems.

The impact of marine ecotourism on reef predators is poorly understood and there is growing concern that overcrowding in Marine Protected Areas (MPAs) may disturb the species that these areas were established to protect. To improve our understanding of this issue, we used acoustic telemetry to examine the relationship between human activity at the Molokini Marine Life Conservation District (MLCD) and the habitat use of five reef-associated predators (Caranx melampygus, Caranx ignobilis, Triaenodon obesus, Carcharhinus amblyrhynchos, and Aprion virscens). During peak hours of human use, there was a negative relationship (R2=0.77, P<0.001) between the presence of bluefin trevally (Caranx melampygus) and vessels in subzone A. No other species showed strong evidence of this relationship. However, our results suggest that during this time, the natural ecosystem function that the reserve was established to protect may be compromised and overcrowding should be considered when managing MPAs.

Wastewater outfall pipes are structures that may attract marine fishes, yet previous studies that address the risks of exposure to wastewater effluent rarely account for the movements of the species studied. This study used acoustic telemetry to quantify the movement patterns and habitat association of demersal species (Citharichthys sordidus, Pleuronichthys verticalis, Parophrys vetulus, Sebastes miniatus) at two sites (near a wastewater outfall and at a reference site) in southern California over one year. Residencies to both sites were low for pleuronectiform fishes (C. sordidus, P. verticalis, P. vetulus, less than 10% of the study duration was spent in either site), which indicates that tissue samples from these species likely reflect the accumulation of contaminants across individuals’ ranges, not just the outfall site. Alternatively, S. miniatus showed higher degrees of residency to the outfall site (nearly 40% of the study duration) and may be the most susceptible to wastewater effluent effects.