Gulf Ecosystem Research Articles

Long-term impact of the Deepwater Horizon oil well blowout on methane oxidation dynamics in the northern Gulf of Mexico

The Deepwater Horizon oil well blowout discharged an unprecedented amount of methane into the water column of the northern Gulf of Mexico between April and July 2010. The methanotrophic community bloomed in response to the sustained methane release, resulting in the highest methane oxidation rates measured in the water column of an open ocean environment to date. To assess the long-term impact and recovery of the northern Gulf of Mexico methanotrophic community, we tracked methane dynamics for five years post-blowout. We determined methane concentration and methane oxidation rates at 31 different sites, resulting in ~900 discrete water column samples across the northern Gulf ecosystem, the largest compilation of methane oxidation rate measurements in an offshore ocean environment. Though methane concentrations approached pre-blowout concentrations within one year, methane oxidation rates exhibited a more gradual trend of decreasing activity. These results suggest that Gulf-wide circulation patterns dispersed and redistributed methanotrophic biomass that bloomed and accumulated in the wake of the Deepwater Horizon blowout, and that this biomass was able to perpetuate elevated methanotrophic activity for multiple years after the blowout at levels above anticipated background rates. This dataset provides a rare view of the response of an ocean ecosystem to a large pulse of methane and reveals unanticipated dynamics of microbial methanotrophy as a result of such human-induced methane releases.

Adaptation of diet in a changed environment: Increased consumption of lobster krill Munida gregaria (Fabricius, 1793) by Argentine hake

AbstractA well‐replicated decadal‐term (2005–2014) stomach content data set was analysed in order to infer inter‐annual fluctuations in the diet of the Argentine hake, Merluccius hubbsi, an opportunistic predator in the San Jorge Gulf (SJG) ecosystem in the Southwest Atlantic. Ten research cruises were carried out each year during January from 2005 to 2014. A total of 18,461 specimens of Me. hubbsi was analysed, of which 6,777 (36.71%) contained food in their stomachs. The diet of Me. hubbsi changed markedly from 2011 onwards, with much greater consumption of the lobster krill Munida gregaria compared to the years before 2011. The frequency of occurrence (%F) of Mu. gregaria in the stomach contents of Argentine hake increased from the year 2009 onwards, most noticeably since 2011, and mostly over the southern region of the SJG. The main predators of Mu. gregaria in the SJG are two species of teleost fish (pink cusk eel, Genypterus blacodes, Argentine seabass, Acanthistius brasilianus) and three Rajidae skates (Zearaja chilensis, Psammobatis spp. and Sympterygia bonapartii), which exhibited decreased catches in the years analysed. The increased consumption of Mu. gregaria by Me. hubbsi, coupled with decreased trends in abundance of the main predators of the lobster krill during the last decade, indicate that top‐down trophic dynamic control occurs in the SJG ecosystem.

Spat Settlement of the Smooth ScallopFlexopecten glaber(Linnaeus, 1758) and Variegated ScallopChlamys varia(Linnaeus, 1758) in Amvrakikos Gulf, Ionian Sea (Northwestern Greece)

ABSTRACT The seasonal variation and spat recruitment pattern of the scallops Flexopecten glaber and Chlamys varia in the protected aquatic ecosystem of the northwestern Amvrakikos Gulf (Natura, 2000) were examined by using a combination of plankton sampling and spat collection techniques during the spring and summer of 2007. The presence of the larvae was reported in all samples from the beginning of May to the end of August. Peak numbers were obtained at the beginning of June and in mid-July. The highest settlement density was recorded at a depth of 8 m below the surface, indicating the most suitable placement for the spat collectors despite the hypoxic bottom layer underneath.

The Role of Wind in Modeling of Oil Pollution Transport and Diffusion in the Persian Gulf

The Persian Gulf ecosystem is facing a variety of stresses as a result of being located within the richest oil province in the world, which hosts more than 67 % of the world oil reserve. In this paper, the distribution of oil pollution on the surface layer of the Persian Gulf is predicted for the different months after the release, based on the Coupled Hydrodynamical Ecological model for Regional Shelf seas (COHERENS). An Eulerian model for the Persian Gulf is set up using the Cartesian coordinate in the horizontal direction, and the sigma coordinate in the vertical direction. Based on this model, our analysis and simulation results indicate that the winds lead to diffusion of the contaminant concentration in the direction of the Arabian coast from the initial position of the spill. The results of this study can be used to provide appropriate solutions for preventing oil from spreading further in the region.

Assessment of Land Cover Change Hotspots in Gulf of Kachchh, India Using Multi-Temporal Remote Sensing Data and GIS

Remote sensing is an indispensable tool for assessing and monitoring land use/land cover changes and supports in planning appropriate conservation measures. This study has analysed the status and distribution of different land use/land cover from 1977 to 2015 and identified the land use/land cover change hotspots in Gulf of Kachchh region, India. The total mangrove area has increased from 140.5 km2 to 700.2 km2 from 1977 to 2015. Among all the different time periods the highest rate of mangrove expansion was found between 2008 to 2011. The results indicate that during the past four decades, mangrove, salt pans and built-up land have been increased by 79.9 %, 84 % and 93.8 % respectively. About 21.4 km2 of mangroves was converted to salt pans and built-up land from 1977 to 2015. Annual rate of afforestation was estimated as 7.01, 12.58, 16.03 and 4.73 for 1999–2006, 2006–2008, 2008–2011 and 2011–2015. Hotspot analysis has identified 33 positive and 11 negative change land cover hotspots in Gulf of Kachchh. Strict management policies are required to prevent further loss of mangroves and conservation of ecologically unique ecosystem of Gulf of Kachchh.

Hercules 265 rapid response: Immediate ecosystem impacts of a natural gas blowout incident

In late July 2013, the Hercules 265 drilling rig in the Northern Gulf of Mexico experienced a catastrophic loss of control. Large quantities of natural gas spewed into the environment for ~2 days before the well self-sealed through down-hole collapse below the seafloor. Ecosystem Impacts of Oil and Gas Inputs to the Gulf (ECOGIG) and collaborating Gulf of Mexico Research Initiative (GoMRI) consortia mounted a rapid response cruise to characterize the waters around the Hercules 265 rig, beginning just 4 days after the blowout. Our analysis showed an immediate microbial response to the elevated concentrations of methane in the water column, as evidenced by the drawdown of oxygen to hypoxic conditions, the incorporation of methane-derived carbon into particles, and measurable rates of methane-assimilation and nitrogen-fixation. Additionally, radium isotope measurements allowed us to constrain the timescale of bottom water exposure to the influence of the rig. A second sampling by the Center for Integrated Modeling and Analysis of Gulf Ecosystems (C-IMAGE) consortium indicated that the ecosystem had returned to near pre-blowout conditions within one month.

Macrobenthos in the central Arabian Gulf: a reflection of climate extremes and variability

The arid subtropical ecosystem of the central Arabian Gulf was used to explore the combined effects of low primary productivity, high salinities, and variable temperatures on the composition and structure of benthic macrofauna at 13 sites encircling the Qatar Peninsula in winter and summer (or late spring) of 2010 and 2011. The low abundance, biomass, and remarkably high species turnover may be a reflection of the oligotrophic, thermally variable, hypersaline coastal environment. The number of species and within-habitat diversity was lowest in the highest salinities but increased with finer-grained sediments and lower salinity. A remarkable temporal variation in species composition observed may reflect insufficient primary production to sustain new populations recruited from the seasonal exchange of water from the adjacent Sea of Oman. Low abundances accompanied by continued replacement of species may be a “new model” for extremely arid conditions associated with global warming.

Ecosystem health of a Mediterranean semi-enclosed embayment (Amvrakikos Gulf, Greece): Assessing changes using a modeling approach

Marine and coastal ecosystems are important for human wellbeing in multiple ways and yet they are subject to increasing anthropogenic stressors which pose serious threats to their health status. In this context, we used an ecosystem modeling approach to assess and quantify the health status of a semi-enclosed embayment of the Mediterranean Sea, the Amvrakikos Gulf (surface: 405km2; maximum depth: 60m) (Ionian Sea). In particular, we built a food web model of the Gulf ecosystem for the 1980 and we fit it to time series from 1980 to 2013. The aim of the study was to: (1) investigate dynamics of marine resources in the last three decades considering the effect of changes in rivers run off, development of fish farming and dynamics of fisheries as the major anthropogenic drivers affecting the system; (2) assess structural and functional changes of the Gulf, using model derived indicators obtained from temporal simulations. Results indicated that the strongest drivers in the Amvrakikos food web were changes in nutrients and organic matter mostly from the loads of two local rivers. Trends in ecological indicators, which explained changes in the structure of the Gulf, highlighted a degradation of the demersal compartments of the food web and a relative stability of the pelagic ones mainly due to high eutrophication levels. By including several ecosystem drivers into the model, the present study is intended as a tool for assessing Amvrakikos ecosystem health and for developing future management policies in the Gulf.

Environmental Niche Overlap between Common and Dusky Dolphins in North Patagonia, Argentina.

Research on the ecology of sympatric dolphins has increased worldwide in recent decades. However, many dolphin associations such as that between common dolphins (Delphinus delphis) and dusky dolphins (Lagenorhynchus obscurus) are poorly understood. The present study was conducted in the San Matías Gulf (SMG) ecosystem (North Patagonia, Argentina) where a high diet overlap among both species was found. The main objective of the present work was to explore the niche overlap of common and dusky dolphins in the habitat and temporal dimensions. The specific aims were (a) to evaluate the habitat use strategies of both species through a comparison of their group attributes (social composition, size and activity), and (b) to evaluate their habitat preferences and habitat overlap through Environmental Niche modeling considering two oceanographic seasons. To accomplish these aims, we used a historic database of opportunistic and systematic records collected from 1983 to 2011. Common and dusky dolphins exhibited similar patterns of group size (from less than 10 to more than 100 individuals), activity (both species use the area to feed, nurse, and copulate), and composition (adults, juveniles, and mothers with calves were observed for both species). Also, both species were observed travelling and feeding in mixed-species groups. Specific overlap indices were higher for common dolphins than for dusky dolphins, but all indices were low, suggesting that they are mainly segregated in the habitat dimension. In the case of common dolphins, the best habitats were located in the northwest of the gulf far from the coast. In the warm season they prefer areas with temperate sea surface and in the cold season they prefer areas with relatively high variability of sea surface temperature. Meanwhile, dusky dolphins prefer areas with steep slopes close to the coast in the southwestern sector of the gulf in both seasons.

Biodegradation of HDPE by Aspergillus spp. from marine ecosystem of Gulf of Mannar, India

High density polyethylene (HDPE) is the most commonly found non-degradable solid waste among the polyethylene. In this present study, HDPE degrading various fungal strains were isolated from the polyethylene waste dumped marine coastal area and screened under in vitro condition. Based on weight loss and FT-IR Spectrophotometric analysis, two fungal strains designated as VRKPT1 and VRKPT2 were found to be efficient in HDPE degradation. Through the sequence analysis of ITS region homology, the isolated fungi were identified as Aspergillus tubingensis VRKPT1 and Aspergillus flavus VRKPT2. The biofilm formation observed under epifluorescent microscope had shown the viability of fungal strains even after one month of incubation. The biodegradation of HDPE film nature was further investigated through SEM analysis. HDPE poses severe environmental threats and hence the ability of fungal isolates was proved to utilize virgin polyethylene as the carbon source without any pre-treatment and pro-oxidant additives.

Bacterial Diversity Associated with Cinachyra cavernosa and Haliclona pigmentifera, Cohabiting Sponges in the Coral Reef Ecosystem of Gulf of Mannar, Southeast Coast of India.

Sponges are abundant, diverse and functionally important organisms of coral reef ecosystems. Sponge-associated microorganisms have been receiving greater attention because of their significant contribution to sponge biomass, biogeochemical cycles and biotechnological potentials. However, our understanding of the sponge microbiome is limited to a few species of sponges from restricted geographical locations. Here, we report for the first time the bacterial diversity of two cohabiting sponges, viz. Cinachyra cavernosa and Haliclona pigmentifera, as well as that in the ambient water from the coral reef ecosystems of the Gulf of Mannar, located along the southeast coast of India. Two hundred and fifty two clones in the 16S rRNA gene library of these sponges were grouped into eight distinct phyla, of which four belonged to the core group that are associated only with sponges. Phylogenetic analysis of the core bacteria showed close affinity to other sponge-associated bacteria from different geographical locations. γ-Proteobacteria, Chloroflexi, Planctomycetes and Deferribacter were the core groups in C. cavernosa while β and δ-Proteobacteria performed this role in H. pigmentifera. We observed greater OTU diversity for C. cavernosa (Hǀ 2.07) compared to H. pigmentifera (Hǀ 1.97). UniFrac analysis confirmed the difference in bacterial diversity of the two sponge species and also between the sponges and the reef water (p<0.001). The results of our study restate the existence of a host driven force in shaping the sponge microbiome.

Assessment of heavy metal contamination in the surface sediments in the mangrove ecosystem of Gulf of Kachchh, West Coast of India

This study was an attempt to understand the role of biogeochemical processes in controlling the heavy metal distribution in the mangroves and to assess heavy metal pollution load (viz. Cr, Fe, Mn, Co, Ni, Cu, Zn, Cd, and Pb) in the Gulf of Kachchh, India. Various biogeochemical processes and anthropogenic factors were playing an important role in altering the concentration of heavy metals in the sediments. A significant correlation of Mn, Fe and Pb with Zn implies the role of diffused anthropogenic activities. The organic carbon content (1.47–3.25 %) and clay content (0.1–2.5 %) seem to play a significant role in the metal concentration. Factor analysis suggested two different processes, Factor I strongly indicating anthropogenic activities and Factor II indicating the combination of natural, marine in situ reduction processes (biogeochemical) with partial anthropogenic influence. The enrichment factor (EF) and Geochemical Index (I geo) of Cu were higher at Old Bedi Port (S5), whereas both these values were higher for Cu as well as Cd at Jam-Salaya (S8). I geo values indicate that sediments around the estuarine mouths were polluted with heavy metals as compared to other locations. Except Chodeshwar (S9), PLI value >1 was reported in almost all the locations, with a slightly higher value reported at Narara (S7); (1.57) and New Bedi Port (S4); (1.56). The findings of this study would help in formulating guidelines for controlling the pollution and suggest the ways by which the mangroves of the Gulf of Kachchh could be revitalized.

The influence of the Guadalquivir river on spatio-temporal variability in the pelagic ecosystem of the eastern Gulf of Cádiz

This study examines the spatio-temporal variability of the turbidity plume and phytoplankton biomass (in terms of chlorophyll) in the marine region influenced by the Guadalquivir estuary using ocean colour images over a period of 11 years (2003-2013). The area of the turbidity plume was calculated using water-leaving radiance at 555 nm (nLw555). Climatologic and monthly averages showed recurrent high nLw555 levels in winter and high chlorophyll in spring. Similar variability was confirmed by Empirical Orthogonal Function (EOF) analysis of 8-day composite images, illustrating the existence of different regions with similar behavior. The first EOF mode explained 60.7% and 31% of the variability in nLw555 and chlorophyll, respectively, and was associated with enhanced Total Suspended Solids (TSS) in autumn-winter and phytoplankton blooms in winter-spring periods. The results confirmed that the development of the turbidity plume and subsequent phytoplankton blooms were strongly regulated by river discharges and precipitation. Indeed, interannual variation in nLw555 was consistent with changes in the large-scale climate index, the North Atlantic Oscillation, a proxy for regional rainfall patterns. In the case of phytoplankton biomass, the second EOF mode revealed differentiation between offshore and nearshore areas, the latter characterized by delayed development of phytoplankton bloom due to light limitation by high TSS. This suggests that the stability of the water column, via its influence on phytoplankton light-limitation, influenced also the timing and magnitude of phytoplankton bloom events. The dynamic of the Guadalquivir estuary turbidity plume is a crucial factor for the pelagic ecosystem of the Eastern Gulf of Cadiz, governing phytoplankton productivity.

Effects of olive oil wastes on river basins and an oligotrophic coastal marine ecosystem: A case study in Greece

This work aims to contribute to the knowledge of the impacts of olive oil waste discharge to freshwater and oligotrophic marine environments, since the ecological impact of olive oil wastes in riverine and coastal marine ecosystems, which are the final repositories of the pollutants, is a great environmental problem on a global scale, mostly concerning all the Mediterranean countries with olive oil production.Messinia, in southwestern Greece, is one of the greatest olive oil production areas in Europe. During the last decade around 1.4×106tons of olive oil mill wastewater has been disposed in the rivers of Messinia and finally entered the marine ecosystem of Messiniakos gulf. The pollution from olive oil mill wastewater in the main rivers of Messinia and the oligotrophic coastal zone of Messiniakos gulf and its effects on marine organisms were evaluated, before, during and after the olive oil production period. Elevated amounts of phenols (36.2–178mgL−1) and high concentrations of ammonium (7.29–18.9mmolL−1) and inorganic phosphorus (0.5–7.48mmolL−1) were measured in small streams where the liquid disposals from several olive oil industries were gathered before their discharge in the major rivers of Messinia. The large number of olive oil units has downgraded the riverine and marine ecosystems during the productive period and a period more than five months is needed for the recovery of the ecosystem. Statistical analysis showed that the enrichment of freshwater and the coastal zone of Messiniakos gulf in ammonia, nitrite, phenols, total organic carbon, copper, manganese and nickel was directly correlated with the wastes from olive oil. Toxicity tests using 24h LC50 Palaemonidae shrimp confirm that olive mill wastewater possesses very high toxicity in the aquatic environment.

Regime shift in the ecosystem of the eastern Gulf of Finland caused by the invasion of the polychaete Marenzelleria arctia

The changes in the concentrations of the mineral nitrogen (nitrates and nitrites) and phosphorus and in the state of the planktic communities in the eastern Gulf of Finland following a largescale invasion of the polychaete Marenzelleria arctia were analyzed. The bioirrigation and bioturbation of the bottom deposits by polychaetes resulted in a dramatic increase in the nitrogen/phosphorus ratio in the waters of the gulf, thus leading to cascade changes in the plankton. As a result of the decrease in the abundance of colonial nitrogen� fixing cyanobacteria, which cause "blooming" in surface waters, the total biomass of the phytoplankton and chlorophyll a concentration decreased. Because of the disappearance of large colonies of cyanobacteria and the surge of small algae, the food supply for the zooplankton improved and its biomass increased. According to our calculations, the amount of phosphorus deposited in the bottom sediments as a result of the polychaete activity markedly exceeded the external phosphorus load on the Gulf of Finland from the Russian coast. We conclude that the invasion of Marenzelleria arctia resulted in the cardinal reconstruction of the entire ecosys� tem of the eastern Gulf of Finland.

Regime Shift in the Ecosystem of the Eastern Gulf of Finland due to Invasion of PolychaetesMarenzelleria arctia

Regime Shift in the Ecosystem of the Eastern Gulf of Finland due to Invasion of PolychaetesMarenzelleria arctia

Indirect Effects of Conservation Policies on the Coupled Human-Natural Ecosystem of the Upper Gulf of California

High bycatch of non-target species and species of conservation concern often drives the implementation of fisheries policies. However, species- or fishery-specific policies may lead to indirect consequences, positive or negative, for other species or fisheries. We use an Atlantis ecosystem model of the Northern Gulf of California to evaluate the effects of fisheries policies directed at reducing bycatch of vaquita (Phocoena sinus) on other species of conservation concern, priority target species, and metrics of ecosystem function and structure. Vaquita, a Critically Endangered porpoise endemic to the Upper Gulf of California, are frequently entangled by finfish gillnets and shrimp driftnets. We tested five fishery management scenarios, projected over 30 years (2008 to 2038), directed at vaquita conservation. The scenarios consider progressively larger spatial restrictions for finfish gillnets and shrimp driftnets. The most restrictive scenario resulted in the highest biomass of species of conservation concern; the scenario without any conservation measures in place resulted in the lowest. Vaquita experienced the largest population increase of any functional group; their biomass increased 2.7 times relative to initial (2008) levels under the most restrictive spatial closure scenario. Bycatch of sea lions, sea turtles, and totoaba decreased > 80% in shrimp driftnets and at least 20% in finfish gillnet fleets under spatial management. We found indirect effects on species and ecosystem function and structure as a result of vaquita management actions. Biomass and catch of forage fish declined, which could affect lower-trophic level fisheries, while other species such as skates, rays, and sharks increased in both biomass and catch. When comparing across performance metrics, we found that scenarios that increased ecosystem function and structure resulted in lower economic performance indicators, underscoring the need for management actions that consider ecological and economic tradeoffs as part of the integrated management of the Upper Gulf of California.

Retrospective of the collaboration between the Aquatic Ecosystem Health and Management Society and Kuwait Institute for Scientific Research

The Aquatic Ecosystem Health and Management Society (AEHMS) has a history of involvement in the study of aquatic ecosystems in the Arabian Gulf Region, and has been actively involved in various activities there for over a decade. For example, the Society was instrumental in conducting sediment toxicity assessment training workshops for the staff and students at the Kuwait Institute for Scientific Research (KISR). This collaboration extended in the formation of a working group whose mission was to publish the first comprehensive peer-reviewed book (The Gulf Ecosystem: Health and Sustainability; Khan et al., 2002) which was sponsored by KISR.The cooperation between KISR and AEHMS continued and resulted in the convening of the GULF II conference “The State of the Gulf Ecosystem: Functioning and Services” in 2011. We worked very closely in the organization of the conference and the resulting publication of a special issue of the Journal, Aquatic Ecosystem Health and Management (“Changing Gulf Ecosystem: Ecology, Health and Management,” AEHM, 2012). Based on the input received it could be concluded that the GULF II conference in Kuwait was productive and highly successful. It included almost 60 oral presentations, 36 posters and 7 keynote speeches. KISR and its staff enjoyed working with the AEHMS and its secretariat, and the collaboration produced excellent results.I’d like to congratulate the AEHMS, its staff, as well as the Executive Committee for their promotion of ecosystem based science in the Middle East, as well as for their hard work to conserve aquatic resources globally.

Aquatic Ecosystem Health and Management Society: A global integration of aquatic ecosystems research and development

Aquatic Ecosystem Health and Management Society: A global integration of aquatic ecosystems research and development

Assessing changes in seawater intrusion and water quality of the Shatt Al-Arab River, Iraq

Many adverse environmental factors influencing the Shatt-al Arab River, southern Iraq, during the past century and especially in recent years, combined with the ever-increasing demand for freshwater in the region, indicate the need to obtain information about its salinity regime. The aim of our study was both to find out what historical data there are and then to compare these with the results of a survey of the salinity and water quality of a stretch of the present river over the year October 2009–September 2010. The evidence suggests that there has been a marked upstream shift in the influence of sea water. Salinity values of 2 and 8‰ were found at two sites where elevated salinity had never been reported previously. Water quality variables indicated increased concentrations over the previous four decades and were beyond the national and international standards. As such changes in a major water resource have serious implications for the inhabitants of Basrah, the biological diversity in the river and the whole Gulf ecosystem, it is suggested that there should be a much more detailed study to provide the evidence needed to convince upstream water users of the need to conserve water and manage the whole catchment properly.