Fresh submarine groundwater discharge (fresh SGD), the efflux of terrestrial groundwater directly into the ocean, is a ubiquitous pathway for nutrient-rich freshwater to coastal ecosystems, altering their hydrography, hydrochemistry, and primary productivity. Yet only little is known about the effects of fresh SGD on the fitness of higher trophic levels such as teleost fish. Otolith analysis revealed that somatic growth rates were significantly higher and settlement to reef habitat took place significantly earlier in juvenile gray demoiselle Chrysiptera glauca exposed to fresh SGD as compared to strictly marine conditions. Contrary to expectations, feeding conditions were comparable in both habitats. We propose that physiologically beneficial environmental conditions brought about by the submarine influx of cold acidic freshwater enabled juvenile fish to exhibit elevated growth rates, thereby increasing their survival potential. This effect would directly link changes in groundwater on land to variations in marine primary and secondary consumer biomass at the coast.
Human Impacts on the Environment
Estimating the potential environmental risks of worldwide coastal recreational navigation on water quality is an important step towards designing a sustainable global market. This study proposes the creation of a global atlas of the environmental risk of marinas on water quality by applying the Marina Environmental Risk Assessment (MERA) procedure. Calculations integrate three main risk factors: Pressure, State and Response. Applying the MERA approach to 105 globally distributed marinas has confirmed the utility, versatility and adaptability of this procedure as a novel tool to compare the environmental risks within and among regions (i.e. for area-based management), to identify the world's best practices (i.e. to optimize existing management) and to understand and adjust global risks in future development (i.e. improved planning).
Marine megafauna (elasmobranchs, marine mammals, turtles, and seabirds) are important ecologically and economically because many species often occupy upper trophic levels as adults and are essential for marine-based tourism in many areas of the world. This group of species is also heavily impacted by fishing because most have late sexual maturity, longevity, and low reproductive output, which affects their ability to recover from depletion. In Galapagos, marine megafauna species are protected from fishing throughout the marine reserve and are the main attraction for marine-based tourism, helping generate millions of dollars in revenue annually. Despite their importance in the archipelago, these species are being caught as bycatch in the multiple artisanal longlining projects that have been carried out since the implementation of the reserve in 1998. Longlining was originally proposed as a way of redirecting fishing effort from the severely depleted coastal-demersal species to pelagic fish such as yellowfin tuna and swordfish. Although all these projects have resulted in high bycatch of megafauna, longline fishing projects have continued without independent scientific studies to evaluate their impact, largely due to poor objective definition, data collection, and enforcement. To fill in this knowledge gap, we analyzed data of the fifth experimental longline fishing project undertaken in 2012–2013 to describe the fishery, identify variables affecting the composition and quantity of bycatch, and suggest mitigation strategies. This experimental project had twelve vessels, which deployed 42,007 hooks catching 4893 individuals of 33 species, mostly yellowfin tuna and swordfish. Of those, 16 species were protected megafauna, particularly blacktip sharks (Carcharhinus limbatus) and oceanic manta (Mobula birostris). These species were regularly captured during the two seasons and in the three bioregions that occur in the archipelago, suggesting little potential to mitigate their catch. As an alternative, we identified 14 hotspots where yellowfin tuna and swordfish could be harvested in large numbers sustainably through more selective fishing techniques such as pole fishing, a method that is also more economical for artisanal fishers. In an archipelago where the main economic activity is marine wildlife tourism, the implementation of an extractive and unselective activity such as pelagic longing fishing should be avoided to ensure the sustainability of the Galapagos marine ecosystem and its booming tourism industry.
A diverse assemblage of adult reef fishes and invertebrates occurs at offshore oil production platforms in the Southern California Bight (SCB). Coincident with the initiation of the decommissioning of six platforms in the SCB, the goal of this study was to examine how a platform's geographical location plays a role in its potential contribution of larval recruits to natural areas. Using a three-dimensional biophysical model, we quantified the potential connectivity of larvae, particularly relevant to reef fishes, from three offshore platforms to four coastal shelf regions where the majority of rocky settlement habitat occurs in the SCB. The regions cover the shelves of the mainland coast and islands and offshore banks in the southern SCB. The main findings indicate that (1) the potential for larval subsidies from platforms in the southern SCB to populations in the northern SCB are greater than the potential for larval subsidies from platforms in the northern SCB to the southern SCB; (2) there is greater seasonal variability of potential connectivity from platforms to the mainland shelf region of the northern SCB than to the mainland shelf region of the southern SCB or shelves around islands and banks; and (3) there is consistency across years in the relative magnitude of potential connectivity from the platforms to the four shelf regions. We conclude that a platform's function as a larval source should be considered an ecological criterion when evaluating whether a platform is to be converted to an artificial reef and implementing marine spatial planning.
Over 60% of the world’s reefs experience damage from local activities such as overfishing, coastal development, and watershed pollution. Land-based sources of pollution are a critical threat to coral reefs, and understanding “ridge-to-reef” changes is urgently needed to improve management and coral survival in the Anthropocene. We review existing literature on spatial-ecological connections between land use and coral health, specifically examining vegetative, agricultural, urban, and other land-use types. In general, forested land use is positively related to metrics of coral condition, while anthropogenic land uses like urban development and agriculture drive a decline in coral cover, diversity, colony size, and structural complexity. However, land-use and land-cover impacts vary across time and space, and small portions of the landscape (e.g., discrete segments of unpaved roads, grazed and scalded hillsides) may have an outsized effect on reef pollution, presenting opportunities for targeted conservation. Some coral species show resilience under land-use and land-cover change, and the impact of land use on coral recovery from bleaching remains an active area of research. Finally, a spatial bibliography of existing literature reveals that most ridge-to-reef studies focus on a handful of regional hotspots, surface water, and watershed-scale dynamics; more research is needed to address groundwater connectivity and to compare land-use impacts across multiple regions and scales. Approaches from landscape ecology that assess spatial patterns of, and synergies between, interlocking land cover may assist conservation managers in designing more resilient reefscapes.
Disposal of mine tailings in marine shallow water ecosystems represents an environmental challenge, and the present paper reports results from a field study in Frænfjorden, Norway, which is subject to such disposal. Structural and functional responses of benthic infauna and epifauna were investigated along a gradient from heavy tailings deposition to reference conditions. The tailings clearly impacted the faunal composition, with lowered species number close to the outfall. Total abundance of infauna increased in the most impacted area due to dominance of opportunistic species, whereas the epifauna was reduced and represented by a few scattered specimens only. In the most impacted area functional responses included an increase in mobile carnivores/omnivores and species utilizing symbionts. Sessile and tube-living taxa, and deposit and suspension feeders decreased, probably due to smothering in combination with tailings-associated changes of the substrate. Functional diversity decreased for both infauna and epifauna, but less than the structural diversity.
We examine the dive and movement behavior of blue, fin, and humpback whales along the US West Coast in regions with high ship traffic where ship strikes have been identified as a major concern. All three species are known to feed in coastal waters near areas of high ship traffic. We analyzed data from 33 archival tag deployments representing over 3,000 h of data that were attached with suction-cups or short darts for periods >20 h and recorded depth (≥ 1 Hz), fast-lock GPS positions and other sensors. There were clear differences among the three species but all showed a distinct diurnal difference in diving behavior. While dive depth varied among animals based on where prey was located, whales spent a high proportion of their time closer to the surface where they would be more vulnerable to ship strikes at night than in the day. This was most pronounced for blue whales where vulnerability was twice as high at night compared to the day. We also found differences in movement patterns of whales between day and night. Movements were more localized to specific areas in the day near prey resources while at night these movements often involved directional movements (though sometimes returning to the same area). We show how in several specific areas like the Santa Barbara Channel, these differences in movements and locations translate to a very different overlap with shipping lanes at night compared to the daytime locations, which is the basis for most sighting data.
Coral reefs are periodically impacted by disturbance events that reduce live coral cover and habitat complexity, with concomitant effects on fish assemblage structure. While the density of some fish species may increase following coral loss, most species decline. Determining which species are ‘winners’ and ‘losers’ following disturbances is fundamental to inform projections of future reef community structure, biodiversity, and productivity. Here, we analyse a long-term (2006–2018), spatially extensive (≈ 700 km) ‘natural experiment’ in which the responses of 11 wrasse taxa to acute disturbance events and no-take marine reserve (NTMR) protection were quantified on fringing coral reefs in the Palm (18°34′ S, 146°29′ E), Whitsunday (20°08′ S, 148°56′ E), and Keppel Island (23°10′ S, 150°57′ E) groups, Great Barrier Reef, Australia. The responses of wrasse densities to benthic habitat change were taxa specific and temporally consistent. Disturbance-mediated reductions in live hard coral cover and/or habitat complexity resulted in density declines for Hemigymnus melapterus, Hemigymnus fasciatus, Cheilinus fasciatus, Labroides spp., Oxycheilinus digramma, and Thalassoma spp. Conversely, Halichoeres spp. densities correlated positively with increased relative cover of sand and rubble, while Stethojulis spp., Anampses spp., Epibulus insidiator, and Bodianus spp. displayed variable responses to habitat changes. No wrasses exhibited an NTMR effect and predator density, irrespective of NTMR status, only influenced five taxa across all island groups. The lack of NTMR effects and variable top-down predator effects suggest that taxa-specific benthic habitat associations were the predominant drivers of wrasse densities on inshore GBR reefs.
There are several environmental and ecological effects of shipping. However, these are rarely assessed in total in the scientific literature. Thus, the aim of this study was to summarize the different impacts of water-based transport on aquatic and nearshore ecosystems and to identify knowledge gaps and areas for future research. The review identified several environmental and ecological consequences within the main impact categories of water discharges, physical impacts, and air emissions. However, although quantitative data on these consequences are generally scarce the shipping contribution to acidification by SOx- and NOx-emissions has been quantified to some extent. There are several knowledge gaps regarding the ecological consequences of, for example, the increasing amount of chemicals transported on water, the spread of non-indigenous species coupled with climate change, and physical impacts such as shipping noise and artificial light. The whole plethora of environmental consequences, as well as potential synergistic effects, should be seriously considered in transport planning.