Environmental exposure to organophosphate esters (OPEs) continues to be a concern. Little is known about their bioaccumulation and trophodynamics, especially in tropical food webs. This study collected seawater and fifteen types of organism from a tropical ecosystem, South China Sea, to investigate the species-specific compositional, bioaccumulation, and trophic transfer of OPEs. The total concentrations of 11 target OPEs (ng/g dw) in the organisms decreased with the increase of their trophic levels in the order: phytoplankton (922) > zooplankton (660) > oysters (309) > crabs (225) > coral tissues (202) > fishes (58.2). The composition profiles (relative abundances) of OPEs were different among the species of organisms, which is likely affected by metabolism and the physicochemical property of OPEs. The trophic biomagnification of tripentyl phosphate (TPTP) in the pelagic food web was unexpected and requires further investigation. The trophic magnification factors (TMFs) of OPEs were generally lower in this tropical aquatic food web than in temperate and frigid aquatic food web. Our analysis suggests that there is a significant positive linear correlation between latitude and TMF. Intakes of OPEs through the consumption of the seafood involved in this work does not pose health risk to adults.
The Great Barrier Reef catchment is located adjacent to the world's largest coral reef system, the Great Barrier Reef, in eastern Queensland, Australia.
This study characterized the geologic and hydrogeologic settings and evaluated the influence of regional faults on groundwater flow. 3D geological models of six regions within the catchment were constructed using drill-log data from >49,000 wells, digital elevation models and surface geological maps. The 3D models were then integrated with potentiometric surface maps and faults data to conceptualize the hydraulic relationships of aquifer units and estimate groundwater development potentials. Potentiometric surfaces and fault orientations were used to conceptualize groundwater flow directions.
New hydrological insights for the region
The 3D geological and hydrogeological characterizations revealed previously unknown faults and aquifer units in the study area. The study found that the central regions consisted of fractured and porous-unconfined aquifers, while confined aquifers, which extend to the coast and likely beyond, were also found in the northern and southern most regions. The orientations of the faults trended in NW-SE directions and could form conduits for south-easterly groundwater flow as opposed to the predominate easterly flow in the porous-unconfined and confined aquifers. The 3D models, aquifer connectivities and geometries provided crucial information to determine groundwater development potentials and offer a first step in developing local and regional groundwater flow and contaminant transport models.
Coastal seas are highly productive systems, providing an array of ecosystem services to humankind, such as processing of nutrient effluents from land and climate regulation. However, coastal ecosystems are threatened by human-induced pressures such as climate change and eutrophication. In the coastal zone, the fluxes and transformations of nutrients and carbon sustaining coastal ecosystem functions and services are strongly regulated by benthic biological and chemical processes. Thus, to understand and quantify how coastal ecosystems respond to environmental change, mechanistic modeling of benthic biogeochemical processes is required. Here, we discuss the present model capabilities to quantitatively describe how benthic fauna drives nutrient and carbon processing in the coastal zone. There are a multitude of modeling approaches of different complexity, but a thorough mechanistic description of benthic-pelagic processes is still hampered by a fundamental lack of scientific understanding of the diverse interactions between the physical, chemical and biological processes that drive biogeochemical fluxes in the coastal zone. Especially shallow systems with long water residence times are sensitive to the activities of benthic organisms. Hence, including and improving the description of benthic biomass and metabolism in sediment diagenetic as well as ecosystem models for such systems is essential to increase our understanding of their response to environmental changes and the role of coastal sediments in nutrient and carbon cycling. Major challenges and research priorities are (1) to couple the dynamics of zoobenthic biomass and metabolism to sediment reactive-transport in models, (2) to test and validate model formulations against real-world data to better incorporate the context-dependency of processes in heterogeneous coastal areas in models and (3) to capture the role of stochastic events.
Predicting the distribution of oil, buoyant plastics, flotsam, and marine organisms near the ocean surface remains a fundamental problem of practical importance. This manuscript synthesizes progress in this area during the time of the Gulf of Mexico Research Initiative (GoMRI; 2012–2019), with an emphasis on the accumulation of floating material into highly concentrated streaks on horizontal scales of meters to 10's of kilometers. Prior to the GoMRI period, two new paradigms emerged: the importance of submesoscale frontal dynamics on the larger scales and of surface-wave-driven Langmuir turbulence on the smaller scales, with a broad transition occurring near 100 m. Rapid progress resulted from the combination of high resolution numerical modeling tools, mostly developed before GoMRI, and new observational techniques developed during GoMRI. Massive deployments of inexpensive and biodegradable satellite-tracked surface drifters combined with aerial tracking of oil surrogates (drift cards) enabled simultaneous observations of surface ocean velocities and dispersion over scales of 10 m to 10's of kilometers. Surface current maps produced by ship-mounted radar and aerial optical remote sensing systems, combined with traditional oceanographic tools, enabled a set of coordinated measurement programs that supported and expanded the new paradigms. Submesoscale fronts caused floating material to both accumulate at fronts and to disperse as they evolved, leading to higher local concentrations, but increased overall dispersion. Analyses confirmed the distinct submesoscale dynamics of this process and the complexity of the resulting fields. Existing tools could be developed into predictive models of submesoscale statistics, but prediction of individual submesoscale features will likely remain limited by data. Away from fronts, measured rates of accumulation of material in and beneath surface windrows was found to be consistent with Langmuir turbulence, but highly dependent on the rise rate of the material and thus, for oil, on the droplet size. Models of this process were developed and tested and could be further developed into predictive tools. Both the submesoscale and Langmuir processes are sensitive to coupling with surface waves and air-sea flux processes. This sensitivity is a promising area for future studies.
Identifying key indicator species, their life cycle dynamics and the multiple driving forces they are affected by is an important step in ecosystem-based management. Similarly important is understanding how environmental changes and trophic interactions shape future trajectories of key species with potential implications for ecosystem state and service provision. We here present a statistical modeling framework to assess and quantify cumulative effects on the long-term dynamics of the copepod Pseudocalanus acuspes, a key species in the Baltic Sea. Our model integrates linear and non-linear responses to changes in life stage density, climate and predation pressure as well as stochastic processes. We use the integrated life cycle model to simulate copepod dynamics under a combination of stressor scenarios and to identify conditions under which population responses are potentially mitigated or magnified. Our novel modeling approach reliably captures the historical P. acuspes population dynamics and allows us to identify females in spring and younger copepodites in summer as stages most sensitive to direct and indirect effects of the main environmental stressors, salinity and temperature. Our model simulations furthermore demonstrate that population responses to stressors are dampened through density effects. Multiple stressor interactions were mostly additive except when acting on the same life stage. Here, negative synergistic and positive dampening effects lead to a lower total population size than expected under additive interactions. As a consequence, we found that a favorable increase of oxygen and phosphate conditions together with a reduction in predation pressure by 50% each could counteract the negative effect of a 25% decrease in salinity by only 6%. Ultimately, our simulations suggest that P. acuspes will most certainly decline under a potential freshening of the Baltic Sea and increasing temperatures, which is conditional on the extent of the assumed climate change. Also the planned nutrient reduction strategy and fishery management plan will not necessarily benefit the temporal development of P. acuspes. Moving forward, there is a growing opportunity for using population modeling in cumulative effects assessments. Our modeling framework can help here as simple tool for species with a discrete life cycle to explore stressor interactions and the safe operating space under future climate change.
The harbor seal (Phoca vitulina richardii) population in the Salish Sea has been at equilibrium since the mid-1990s. This stable population of marine mammals resides relatively close to shore near a large human population and offers a novel opportunity to evaluate whether disease acts in a density-dependent manner to limit population growth. We conducted a retrospective analysis of harbor seal stranding and necropsy findings in the San Juan Islands sub-population to assess age-related stranding trends and causes of mortality. Between January 01, 2002 and December 31, 2018, we detected 882 harbor seals that stranded and died in San Juan County and conducted necropsies on 244 of these animals to determine primary and contributing causes of death. Age-related seasonal patterns of stranded animals were evident, with pups found in the summer, weaned pups primarily recovered during fall, and adults and sub-adults recovered in summer and fall. Pups were the most vulnerable to mortality (64% of strandings). Pups predominantly died of nutritional causes (emaciation) (70%), whereas sub-adults and adults presented primarily with clinical signs and gross lesions of infectious disease (42%) and with non-anthropogenic trauma (27%). Primary causes of weaned pup mortality were distributed equally among nutritional, infectious, non-anthropogenic trauma, and anthropogenic trauma categories. Nutritional causes of mortality in pups were likely related to limitations in mid- and late-gestational maternal nutrition, post-partum mismothering, or maternal separation possibly related to human disturbance. Infectious causes were contributing factors in 33% of pups dying of nutritional causes (primarily emaciation–malnutrition syndrome), suggesting an interaction between poor nutritional condition and enhanced susceptibility to infectious diseases. Additional primary causes of harbor seal mortality were related to congenital disorders, predation, human interaction, and infections, including zoonotic and multidrug-resistant pathogens. Bottom-up nutritional limitations for pups, in part possibly related to human disturbance, as well as top-down predatory influences (likely under-represented through strandings) and infectious disease, are important regulators of population growth in this stable, recovered marine mammal population.
The search for potential investors in the conversion of ocean thermal energy to power or hydrogen, and its spinoff projects in Malaysia and the region, continues. In the meantime, several pre-feasibility studies have been completed for selected sites, including that of Pulau Layang-Layang and Pulau Kalumpang (Sabah, Malaysia); Timor-Leste, and off Pulau Weh (Aceh, Indonesia). Various research projects have been completed such as the conversion of solar-thermal to the chilled-water system; the cooling of tropical soils for the culture of temperate crops; the design of offshore structure off the continental slope; hydrogen fuel production and distribution, deep seawater properties to reduce obesity, cholesterol and blood pressure; and the legal-institutional framework for the development of ocean thermal energy conversion. UTM Ocean Thermal Energy Centre (UTM OTEC) has entered into the Collaborative Research Agreement with the Institute of Ocean Energy of Saga University (Japan) to undertake joint research for the development of an experimental rig that introduces a hybrid system with stainless steel heat exchanger. Other aspects of this joint research would include a new design for 3 kW turbine, the introduction of nano-working fluids, the eDNA of intake waters, and improved productivity in the culture of high-value marine produce and products.
This study presents the results of the first broad-scale, spatial cumulative impact analysis (SCIA) conducted for colonial-nesting seabirds at-sea in eastern Canada. Species distribution models, based on at-sea tracking data for thirteen species/groups of seabirds (n = 520 individuals), were applied to over 5000 species-specific colonies to map relative abundance patterns across the entire region. This information was combined with distributional data for a number of key anthropogenic threats to quantify exposure to fisheries, light and ship-source oil pollution, and marine traffic. As a final step, information about species-specific sensitivity to each threat was integrated to compute region-wide cumulative risk.
The data products permit the visualization of the interaction between species and threats, and confirm that large portions of the coastal zones of Nova Scotia and Newfoundland, as well as the Grand Banks shelf break, constitute areas where breeding seabirds experience the highest potential impact. The cumulative risk maps revealed that species which were either widespread throughout coastal areas (e.g., gulls), or capable of foraging long distance (Leach's Storm-Petrel), were most at risk. Cumulative risk maps help identify appropriate and potentially effective management and conservation actions, and are of value to federal regulators responsible for managing cumulative effects as part of the new Canadian Impact Assessment Act. They also can assist marine planners achieve the Aichi marine conservation targets as specified by the Convention on Biodiversity. By filling a knowledge gap for a large potion of the northwest Atlantic, these results help to counter the “shifting baselines syndrome”.
Climate change is altering the intensity and variability of environmental stress that organisms and ecosystems experience, but effects of changing stress regimes are not well understood. We examined impacts of constant and variable sublethal hypoxia exposures on multiple biological processes in the sea urchin Strongylocentrotus purpuratus, a key grazer in California Current kelp forests, which experience high variability in physical conditions. We quantified metabolic rates, grazing, growth, calcification, spine regeneration, and gonad production under constant, 3-hour variable, and 6-hour variable exposures to sublethal hypoxia, and compared responses for each hypoxia regime to normoxic conditions. Sea urchins in constant hypoxia maintained baseline metabolic rates, but had lower grazing, gonad development, and calcification rates than those in ambient conditions. The sublethal impacts of variable hypoxia differed among biological processes. Spine regrowth was reduced under all hypoxia treatments, calcification rates under variable hypoxia were intermediate between normoxia and constant hypoxia, and gonad production correlated negatively with continuous time under hypoxia. Therefore, exposure variability can differentially modulate the impacts of sublethal hypoxia, and may impact sea urchin populations and ecosystems via reduced feeding and reproduction. Addressing realistic, multifaceted stressor exposures and multiple biological responses is crucial for understanding climate change impacts on species and ecosystems.
The California Current Ecosystem (CCE) is a dynamic marine ecosystem from which many socioeconomically important fisheries species are harvested. Here, a genotyping-by-sequencing (GBS) approach was used to examine genomic variation in an early life stage (megalopae) of the Dungeness crab (Cancer magister), which constitutes the most valuable single-species commercial fishery in the CCE. Variation in abundance and timing of megalopae recruitment has been extensively studied for over two decades in Coos Bay, Oregon, United States. Within the CCE, documented timing of Dungeness crab life history events indicates that coastal megalopae recruitment is expected to occur April through July; however, long-term studies in Coos Bay have observed late-season recruitment from August to October. Based on variation at 1,913 presumably neutral loci, evidence was found for weak, yet significant differentiation (FST estimate = 0.0011) between the 2014 expected-season recruits (n = 47) and late-season recruits (n = 47) collected in Coos Bay. However, two putatively adaptive loci with a high FSTestimate (0.2036) between expected-season and late-season recruits were identified. These findings support the hypothesis that expected-season and late-season megalopae recruiting to Coos Bay within the same year may have originated from different locations or from different breeding groups. Understanding marine species connectivity between ecosystems is important when considering how future changes in ocean conditions may impact fishery harvests.