Implications For Marine Ecosystems Research Articles

Assessment of water quality and heavy metal contamination in ballast water: Implications for marine ecosystems and human health

The global menace of non-compliance with ballast water management poses a pressing environmental threat, as it facilitates the transfer of harmful organisms and sediment contaminants. This study investigates the environmental impact of ballast water discharged by ships, focusing on water quality and heavy metal concentrations. The release of ballast water, often containing elevated levels of heavy metals like mercury, lead, and cadmium, poses a significant threat to marine ecosystems. The research, involving water sample collection from ten different vessels across various countries, assesses physicochemical parameters and heavy metal concentrations. Results indicate variations in temperature, turbidity, conductivity, dissolved oxygen, and pH levels among samples. Turbidity values surpassing WHO limits suggest potential anthropogenic pollution. The study identifies significant differences in pH values, potentially influencing microbial populations. Total dissolved solids and total suspended solids values vary, affecting the distribution of potential pathogens. The results reveal varying total concentrations of heavy metals (mg/L) in the following decreasing order: SA>SE>SF>SB>SC>SD>SH>SI>SG>SJ(6.07 >4.95 > 2.07 > 1.59>0.24>1.22>0.09>0.04>0.03>0.01). The highest concentration of heavy metals is recorded for iron (SA= 5.78), zinc (mg/L) (SB = 1.36, SE = 1.30, and SF = 1.35) and lead (Pb) (SE = 2.39). The elevated iron levels in vessels from SA are potentially linked to corrosion processes. Cadmium, lead, and nickel were not detected, except for lead in the sample from SE. Copper concentrations were aligned with EU standards in the vessels. Proper ballast water management is vital for monitoring water qualities, preventing environmental spread of heavy metals, ensuring marine ecosystem health, and developing compliance strategies for ships docking in ports. Highlights Global shipping causes heavy metal pollution, affecting human and ecosystem health Physicochemical parameters variations suggest potential pollution and microbial impact Mercury, lead, and cadmium in ballast water (BW) pose threats to marine ecosystems Increased iron levels could be associated with corrosion processes Effective BW management is crucial for environmental conservation

Climate Change and Ocean Acidification: Unraveling the Complex Interactions and Implications for Marine Ecosystems

Purpose: The study aims to investigate the intricate relationship between ocean acidification and climate change, providing insights into their impacts on marine ecosystems. It seeks to identify sources of greenhouse gases, assess reef vulnerability, and analyze temperature changes' effects on marine biodiversity.
 Methodology: Quantitative research methods are employed, utilizing data from Bangladesh, the USA, India, and the UK. Dynamic patterns in coral reef health, ocean acidification, greenhouse gas emissions, and marine ecosystem health are assessed between 2019 and 2023. Qualitative analysis supplements the quantitative findings, enhancing understanding of climate change's impacts on marine ecosystems and mitigation strategies.
 Findings: The study reveals clear patterns in the countries studied, emphasizing the urgency for continuous monitoring and protection of marine ecosystems. It provides insights into how climate change affects marine ecosystems, triggers ocean acidification, and identifies sources of greenhouse gas emissions. The research underscores the necessity for collaborative efforts to address climate change impacts and promote ecosystem resilience.
 Unique Contribution to Theory, Practice, and Policy: The study contributes to a better understanding of the complex dynamics between ocean acidification, climate change, and marine ecosystems. It offers valuable insights to inform conservation initiatives, policy decisions, and strategies aimed at mitigating adverse impacts on marine species. By highlighting the importance of collective action, the research advocates for a comprehensive approach to address climate change's effects on ecosystems and oceans, fostering resilience and sustainability.

Impacts of Marine Heatwave Events on Three Distinct Upwelling Systems and Their Implications for Marine Ecosystems in the Northwestern South China Sea

Under global warming, the frequency and intensity of marine heatwaves are increasing. However, the inhibition of atmospheric-forcing marine heatwaves (AMHW) on upwelling and their impacts on marine ecosystems remain poorly understood. To address this issue, the satellite sea surface temperature and reanalysis data during 1998–2021 were analyzed in three distinct upwelling systems, in the northwestern South China Sea. The results showed that the coastal tide-induced upwelling in the west (W) of Hainan Island is primarily suppressed by enhanced stratification during the AMHW events, since the coastal tide-induced upwelling is insensitive to wind weakening. Contrarily, the wind-driven upwelling in the east (E) and northeast (NE) of Hainan Island are jointly regulated by wind and stratification during the AMHW. Specifically, the AMHW events have a stronger inhibitory effect on the upwelling and phytoplankton growth in the NE than that in the E. The causes could be the following: (1) the background upwelling in the NE region is stronger than in the E; thus, the NE region has a higher susceptibility to the wind weakening; (2) the wind-driven upwelling begins to be suppressed by AMHW when the high-pressure system is aligned with the coastline of the upwelling. In the NE region, the location of the high-pressure center during the occurrence of AMHW is positioned in closer proximity to the upwelling area. Moreover, the inhibitory effect of wind weakening and stratification enhancing on upwelling changes with the development of the AMHW. Before and during the mature phase of AMHW, stratification and wind jointly inhibit upwelling and phytoplankton growth, while a shift to stratification-dominated (>85%) occurs during the decline phase. This study suggests that MHW has a great impact on the upwelling ecosystem, especially the wind-driven upwelling, which should be given high attention under global warming (with increasing MHW events in the future).

Exploring cosmopolitan jellyfish (Aurelia spp.) bloom dynamics and ecological implications in subtropical waters with mechanistic dynamic modeling

Worldwide massive outbreaks of gelatinous zooplankton have drawn much attention to seeking relevant mechanisms and processes for better management and conservation of ocean ecosystems. In the present study, we developed an individual-based model (IBM) for cosmopolitan jellyfish Aurelia spp., which incorporates a fully coupled pelagic-benthic life cycle with fine-scaled (0.5° × 0.5°) dynamic ocean conditions to examine the spatio-temporal population dynamics of the species in the northern Gulf of Mexico (GoM) from 1995 to 2010. Model simulations highlighted the significant bottom-up effect of environmental conditions in triggering strobilation and subsequent jellyfish blooms. Dynamics of jellyfish populations exhibited large variability in time and space over the northern GoM continental shelf. Simulation results showed that the South Texas coast, the East Louisiana shelf, and the Mississippi Sound were potential bloom hotspots with distinctive driving processes. A case study of the Mississippi Sound region in 2008 revealed a mismatch of bloom timing whether defined as abundance or biomass, which spotlighted the need to further assess the consequence and ecological implication of jellyfish outbreaks to the biomass and energy flows in the ocean. Given that the GoM is vulnerable to jellyfish blooms, findings of this study contribute to the improved understanding of mechanisms and processes of jellyfish blooms with predictions of the status, trend, and hotspots of jellyfish population dynamics under variable environmental conditions and a changing climate. • Significant bottom-up effects that trigger strobilation and blooms of Aurelia spp. were identified. • Stage-structured dynamics of the species show space and time variability across the GoM continental shelf. • Jellyfish bloom hotspots on the GoM continental shelf coincide with particular oceanographic conditions. • Mismatched timing in jellyfish bloom abundance and biomass has implications for marine ecosystems.

Identifying Metocean Drivers of Turbidity Using 18 Years of MODIS Satellite Data: Implications for Marine Ecosystems under Climate Change

Turbidity impacts the growth and productivity of marine benthic habitats due to light limitation. Daily/monthly synoptic and tidal influences often drive turbidity fluctuations, however, our understanding of what drives turbidity across seasonal/interannual timescales is often limited, thus impeding our ability to forecast climate change impacts to ecologically significant habitats. Here, we analysed long term (18-year) MODIS-aqua data to derive turbidity and the associated meteorological and oceanographic (metocean) processes in an arid tropical embayment (Exmouth Gulf in Western Australia) within the eastern Indian Ocean. We found turbidity was associated with El Niño Southern Oscillation (ENSO) cycles as well as Indian Ocean Dipole (IOD) events. Winds from the adjacent terrestrial region were also associated with turbidity and an upward trend in turbidity was evident in the body of the gulf over the 18 years. Our results identify hydrological processes that could be affected by global climate cycles undergoing change and reveal opportunities for managers to reduce impacts to ecologically important ecosystems.

Upwelling Amplifies Ocean Acidification on the East Australian Shelf: Implications for Marine Ecosystems

Frequent upwelling of cold deep water rich in dissolved inorganic nutrients but low in oxygen concentrations and pH is well documented in so-called Eastern-boundary systems. As a consequence vast areas of the continental shelf can turn corrosive to the mineral aragonite, vital to a number of marine organisms. This phenomenon is projected to become more severe with ongoing ocean acidification. Although upwelling is also known to occur in Western-boundary systems, the impact on present day aragonite saturation state (Ω arag ) is virtually unknown, let alone for the decades to come. Here we identified 37 events during 18 weeks of continuous measurements in Cape Byron Marine Park, Australia, by prolonged drops in ocean temperature of up to 5 ◦ C, oxygen concentrations by 34%, pH by 0.12 and Ω_arag by 0.9 units in a matter of hours. Extrapolating present day upwelling to a Pre-Industrial setting shows that ongoing ocean acidification has already lead to the crossing of a number of biological and geochemcial Ω_arag thresholds. If representative for the East Australian shelf, modelling further suggests that coral reefs with low coral cover could become net dissolving within the next 30 years. With the Great Barrier Reef estimated to currently contribute more than A$6 billion annually to the Australian economy, this would come at a considerable financial cost.

Radiocarbon evidence for mid-late Holocene changes in southwest Pacific Ocean circulation

Variability in the southwest (SW) Pacific Ocean circulation is influenced by the changes in the South Pacific subtropical gyre and its western boundary current, the East Australian Current (EAC). The EAC plays a significant role in transporting warm, well-ventilated, nutrient-poor waters to more temperate higher latitudes. Recent climate changes associated with EAC intensification have led to anomalous warming in the South Tasman, with implications for marine ecosystems and environment. A clear understanding of the significance of these changes requires knowledge of past natural variability. Here we have reconstructed a 4500 year record of regional sea surface radiocarbon reservoir ages (R) and local reservoir effects (ΔR). Our results reveal the centennial-scale variability over the last 4500 years, with R ranges as large as 390 14C yr. Older R (~410 14C yr) between 1610 to 1860 A.D. in our record, corresponding to the “Little Ice Age,” suggests a weaker influence of the EAC in the South Tasman. Between 4000 and 1900 cal years B.P., R and ΔR were significantly younger than the modern, with values of ~170 and −130 14C yr, respectively, indicating increased EAC transport of tropical waters into the South Tasman. We propose that the large R variability was influenced by strong and abrupt El Nino events which punctuated the muted El Nino–Southern Oscillation (ENSO) period in the mid-late Holocene and enabled increased westward flow of gyre waters into the SW Pacific. The strengthening of the EAC extension appears to have been a response to the precession-modulated ENSO-Southern Annular Mode interactions.

Marine Renewable Energies: Perspectives and Implications for Marine Ecosystems

Countries with coastlines may have valuable renewable energy resources in the form of tides, currents, waves, and offshore wind. The potential to gather energy from the sea has recently gained interest in several nations [1–3], so Marine Renewable Energy Installations (hereinafter MREIs) will likely become very diffuse in the near future and determine a further transformation of our coastal seas.

Ocean acidification and warming decrease calcification in the crustose coralline alga Hydrolithon onkodes and increase susceptibility to grazing

Anthropogenic CO2 emissions have exacerbated two environmental stressors, global climate warming and ocean acidification (OA), that have serious implications for marine ecosystems. Coral reefs are vulnerable to climate change yet few studies have explored the potential for interactive effects of warming temperature and OA on an important coral reef calcifier, crustose coralline algae (CCA). Coralline algae serve many important ecosystem functions on coral reefs and are one of the most sensitive organisms to ocean acidification. We investigated the effects of elevated pCO2 and temperature on calcification of Hydrolithon onkodes, an important species of reef-building coralline algae, and the subsequent effects on susceptibility to grazing by sea urchins. H. onkodes was exposed to a fully factorial combination of pCO2 (420, 530, 830μatm) and temperature (26, 29°C) treatments, and calcification was measured by the change in buoyant weight after 21days of treatment exposure. Temperature and pCO2 had a significant interactive effect on net calcification of H. onkodes that was driven by the increased calcification response to moderately elevated pCO2. We demonstrate that the CCA calcification response was variable and non-linear, and that there was a trend for highest calcification at ambient temperature. H. onkodes then was exposed to grazing by the sea urchin Echinothrix diadema, and grazing was quantified by the change in CCA buoyant weight from grazing trials. E. diadema removed 60% more CaCO3 from H. onkodes grown at high temperature and high pCO2 than at ambient temperature and low pCO2. The increased susceptibility to grazing in the high pCO2 treatment is among the first evidence indicating the potential for cascading effects of OA and temperature on coral reef organisms and their ecological interactions.

Decadal changes in the South Pacific western boundary current system revealed in observations and ocean state estimates

Observations and ocean state estimates are used to investigate the nature and mechanism of decadal variability in the East Australian Current (EAC) system and South Pacific subtropical gyre. A 62 year record on the Tasmanian continental shelf shows decadal variations of temperature and salinity, as well as a long-term trend, which has been related to wind-driven variations in the poleward extension of the EAC. Repeat expendable bathythermograph lines spanning the last 15 years suggest that low-frequency variations in the transport of the EAC extension and Tasman Front are anticorrelated, but the time series are too short to draw firm conclusions. Here we use two ocean state estimates spanning the past 50 years to diagnose the physical mechanisms and spatial structure of the decadal variability of the South Pacific subtropical gyre. The observations and state estimates paint a consistent picture of the decadal variability of the gyre and EAC system. Strengthening of the basin-wide wind stress curl drives a southward expansion of the subtropical gyre. As the gyre shifts south, the EAC extension pathway is favored at the expense of the Tasman Front, resulting in the observed anticorrelation of the these two major currents. The results suggest that the subtropical gyre and western boundary current respond to decadal variability in basin-scale wind stress curl, consistent with Island Rule dynamics; that strong decadal variability of the South Pacific gyre complicates efforts to infer trends from short-term records; and that wind stress curl changes over the South Pacific basin drive changes in the EAC system that are likely to have implications for marine ecosystems and regional climate.

Winter-Spring flushing of Bass Strait, South-Eastern Australia: a numerical modelling study

This study investigates winter-spring flushing of Bass Strait with a two dimensional non-linear depth-averaged shallow-water model. The model is driven with a 180-day wind time-series. An advection-diffusion scheme for several tracers is used to reveal the flushing pattern/timescale of the region. The study considers how external water masses flush strait waters. It shows that shelf-water entering the strait through the passage between King Island and Cape Grim makes the largest contribution to strait waters. Results show that the central area of the strait is a stagnation-area of weak currents and long flushing times (>160 days). The influence of external water masses on the stagnation-area is estimated. The findings have implications for marine ecosystems, residence times, air-sea modifications of water mass properties and dense water formation in the region.

Quantitative ecosystem indicators for fisheries management

Spring in Paris (31 March to 3 April 2004) helped to attract more than 250 participants from 53 countries to a symposium on ‘‘Quantitative Ecosystem Indicators for Fisheries Management’’. The symposium was hosted by the Intergovernmental Oceanographic Commission at the UNESCO headquarters next to the Eiffel Tower, and coorganized with the Scientific Committee on Oceanic Research (SCOR). Four years of preparation had borne fruit, and the stage was set with a programme of 40 presentations and nearly 150 posters. The symposium was centred on using ecosystem indicators for fisheries management, and as such reflects the growing understanding that exploited fish populations must be considered as integral components of ecosystem function, rather than units that operate independently of their environment. Internationally, there has been wide recognition of the need to move towards an ecosystem approach to fisheries, a development spearheaded by FAO through their Code of Conduct for Responsible Fisheries (Garcia, 2000), and supported by many regional and national institutions as well as academia, NGOs, and the general public. Intergovernmental organizations providing management advice, such as ICES and PICES, require meaningful indicators that adequately reflect the state of marine ecosystems. As we move to embrace an ecosystem perspective, we need new measuring sticks. Ecosystem approaches to fisheries require consideration of the interdependent way we utilize ecosystems. At a minimum, the components to be addressed cover ecological, economic, social, technological, and governance aspects. When considering the ecosystem, we must include not only target species, but also their effects on dependent or competing non-target species, as well as on the habitats shared by the species. An important question thus arises, related to trade-offs. Management interventions directed at one target species may have consequences for many other species, including some that are targets of other fisheries. How do we evaluate the trade-offs involved, and how do we determine the direction that a society should take, based on the implications for marine ecosystems? To answer such questions, analyses must be based on

The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems

Stevens, J. D., Bonfil, R., Dulvy, N. K., and Walker, P. A. 2000. The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems. – ICES Journal of Marine Science, 57: 476–494. The impact of fishing on chondrichthyan stocks around the world is currently the focus of considerable international concern. Most chondrichthyan populations are of low productivity relative to teleost fishes, a consequence of their different life-history strategies. This is reflected in the poor record of sustainability of target shark fisheries. Most sharks and some batoids are predators at, or near, the top of marine food webs. The effects of fishing are examined at the single-species level and through trophic interactions. We summarize the status of chondrichthyan fisheries from around the world. Some 50% of the estimated global catch of chondrichthyans is taken as by-catch, does not appear in official fishery statistics, and is almost totally unmanaged. When taken as by-catch, they are often subjected to high fishing mortality directed at teleost target species. Consequently, some skates, sawfish, and deep-water dogfish have been virtually extirpated from large regions. Some chondrichthyans are more resilient to fishing and we examine predictions on the vulnerability of different species based on their life-history and population parameters. At the species level, fishing may alter size structure and population parameters in response to changes in species abundance. We review the evidence for such density-dependent change. Fishing can affect trophic interactions and we examine cases of apparent species replacement and shifts in community composition. Sharks and rays learn to associate trawlers with food and feeding on discards may increase their populations. Using ECOSIM, we make some predictions about the long-term response of ecosystems to fishing on sharks. Three different environments are analysed: a tropical shelf ecosystem in Venezuela, a Hawaiian coral reef ecosystem, and a North Pacific oceanic ecosystem. 2000 International Council for the Exploration of the Sea