Journal of Sea Research最新文献

With the entry into force of the International Maritime Organization's International Ballast Water Management Convention in September 2017, ships have begun to install and operate onboard ballast water management systems (BWMS) to reduce the number of live organisms in ballast water. Scientific methods were developed to assess the effectiveness of BWMS at reducing the number of live organisms in ballast water. However, detecting low organism concentrations in treated ballast water is challenging when considering the small sample volume (6 mL) analyzed for organisms in the 10–50 μm size class. The volume analyzed can be increased by concentrating the sample prior to analysis, but it is important to assess the effects of the sample concentration method due to potential cell loss experienced during the concentration step. Therefore, laboratory experiments were conducted to assess the effects of a gravity filtration method to concentrate samples to a factor of 40:1. Experiments were conducted for both low and high organism abundances. For unpreserved samples at low organism abundances (∼10 cells mL⁻¹), concentrated samples had on average 31% fewer live cells mL⁻¹ than unconcentrated samples for four out of five experiments. At high organism abundances (≥ 120 cells mL⁻¹), unpreserved concentrated samples had on average 55% fewer live cells than unconcentrated samples. Alternatively, with preserved samples at low organism abundances, concentrated samples had on average 4.5× more cells than unconcentrated samples. At high organism abundances, concentrated samples had on average 6.4× more cells than unconcentrated samples. Differences were also observed between preserved and unpreserved samples. These findings can help to improve ballast water monitoring procedures and BWMS assessments, addressing a critical challenge to maritime environmental protection.

In the past, a large part of the seabed of the southern North Sea was covered by hard substrates, including oyster beds, coarse peat banks, and glacial erratics. Human activities, particularly bottom trawl fisheries, led to the disappearance of most of these hard substrates, resulting in the loss of its associated diverse benthic life as well. However, the introduction of human-made structures such as offshore wind farms in the North Sea, offers a chance to provide habitat of similar functionality as the former hard substrates. The offshore wind farm infrastructure generally contains layers of rock material deployed at the base of the wind turbine foundations and cable crossings, so-called scour protection, aiming to prevent seabed erosion. The scour protection offers a unique habitat for rock-dwelling benthic organisms in an otherwise mostly soft-bottom environment. By designing the scour protection to be more nature-inclusive, the biodiversity of benthic life can be increased. In this study we examined the effect of substrate material and grading of the scour protection on the epibenthic biodiversity in situ. This was done by deploying research cages containing crates (n = 15) with different types of substrates (concrete, granite, and marble) on the scour protection within an offshore wind farm in the Dutch North Sea. The study revealed a significant (p < 0.05) positive relation between available substrate surface (pebble size) and taxonomic richness. Furthermore, a biological trait assessment of living habits (Tube dwelling, Burrowing, Free living, Crevice dwelling, Epi/endobiotic, and Attached) revealed variations in habit modes across substrate types, with marble and concrete samples showing greatest divergence. Marble samples contained a higher prevalence of tube dwelling organisms, whereas concrete samples contained a relatively higher prevalence of free living, epi/endobiotic and crevice dwelling organisms. The findings support the value of nature-inclusive scour protection designs, emphasizing that both taxonomic and functional diversity can be enhanced by increasing the available surface area of the scour protection and incorporating a variety of substrate types. By adopting these nature-inclusive design components, the coexistence of renewable energy production and a diverse marine benthic community can be further optimized.

Dynamic influences of ocean processes on distribution, abundance, and diversity of zooplankton communities were studied over the continental shelf in the northern Gulf of Mexico (GoM) from 2015 to 2017. Zooplankton sampling was conducted on four summer cruises in the northcentral GoM. Sampling was designed in waters potentially influenced by the Loop Current (LC) and/or Mississippi River discharge to assess the impacts of these two mesoscale features on the abundance and diversity of zooplankton. During the three-year study, the LC displayed distinct spatial-temporal variations in penetration and occurrence in the northern GoM. Environmental conditions (i.e., sea surface temperature, salinity, and dissolved oxygen) varied between months and years sampled, and were significantly different among cruises (ANOVA, p < 0.001). The majority of zooplankton consisted of calanoid copepods (65% ± 7.2%, mean ± SD), while non-copepod taxa were primarily chaetognaths, polychaetes, tunicates, and ostracods (23 ± 9.2%). Species abundance and diversity of zooplankton were significantly correlated with sea surface temperature, salinity, and dissolved oxygen (p < 0.05). Canonical correspondence analysis displayed significant associations between mesoscale features and dominant zooplankton groups among cruises and by taxa (Monte Carlo Permutation Test, p < 0.001). In addition, non-metric multidimensional scaling indicated that zooplankton assemblages were distinct, likely caused by Mississippi River plumes during the study period. As one of the few efforts to examine zooplankton dynamics at a low taxon level over the GoM continental shelf regarding the impact of mesoscale features, this study revealed seasonal (i.e. summer) and spatial patterns in distribution, abundance, and diversity of zooplankton communities subjected to the dynamic physicochemical conditions in the northern GoM, which will continue in a changing climate.

The delimitation of fish stocks and how species use habitats are essential keys to develop and to implement fishery resources management and rational sustainable programs. Otolith shape and microchemistry analyses can provide helpful information for defining population units and solving ecological connectivity issues. The black drum, Pogonias courbina, is an important fishery resource in the southeastern Brazil lagoon systems, and is considered a vulnerable fish according to the IUCN Red List of Threatened Species. Thus, the present study aimed to understand the population structure and habitat connectivity of P. courbina in two lagoon systems in the south-east coast of Rio de Janeiro, Brazil. A total of 60 individuals were collected from the lagoons of Saquarema (SQ) and Araruama (AR), between November 2019 and April 2020. Thirty individuals from each location, all estimated to be two years old based on the counting of the annual growth increments, were used. The composition (multi-elemental signatures – MES) and shape (elliptic Fourier descriptors – EFD) of the sagittal otoliths were integrated to evaluate the population structure and the habitat connectivity of the fish inside these lagoon systems. EFD showed differences between lagoon systems, with an overall reclassification rate of 97%. The MES exhibited distinct patterns between lagoon systems, mainly driven by differences in Ba/Ca, Co/Ca, Li/Ca, Mg/Ca, Ni/Ca, Sr/Ca, and Zn/Ca ratios. The overall reclassification rate for MES was also 97% (93% and 100% for SQ and ARA, respectively). The overall reclassification rate obtained using both EFD and MES was 98%. The results suggest a clear spatial discrimination and low connectivity between these groups of two years old P. coubina individuals living in the studied lagoon systems. These findings imply that small-scale artisanal fisheries in the lagoon systems require more attention, aiming to maximize local management strategies for commercially exploited species.

Biological monitoring of planktonic animals is greatly dependent on the deployment of traps. A variety of specialized traps have been designed for surface plankton and vertebrates. However, certain groups, such as planktonic larvae of benthic marine invertebrates remain underrepresented in sampling efforts. Catching them has proven to be more challenging because of their size, swimming ability, location, and abundance. In the present study a successful light trap for sampling American lobster larvae in New Brunswick, Canada, is evaluated on the island of Helgoland (German Bight, North Sea). Our results showed the traps were successful in catching larvae in laboratory experiments but were unable to catch European lobster larvae in the field. Traps deployed in the field were successful in capturing other benthic and pelagic zooplankton predominantly consisting of crustaceans from the orders: Cumacea, Amphipoda, Mysida and Isopoda. The low density of lobster larvae, the island's topography, and their unique photactic response possibly limited the success rate of the light traps. Future research is needed to construct a specialized trap to sample Helgoland's lobster larvae and provide information on the current larval fitness and population numbers.

The number of offshore artificial structures in the North Sea is continuously increasing. Apart from the structures that have been added to the marine environment accidentally (e.g., shipwrecks), structures are also deliberately developed to meet the increasing needs for renewable energy. These structures provide habitat for fouling organisms. The fouling communities vary in abundance and composition based on location, depth, and structure age. Most fouling species filter particles from the water column, changing phytoplankton production and affecting larval settlement success, while releasing ammonium that can fuel phytoplankton growth as well as (pseudo)faeces that enriches the seabed, changing local biogeochemical cycles.

Our study used in-situ incubation chambers to investigate oxygen, nitrogen, and phosphate fluxes associated with fouling organisms to improve understanding of these changes in biogeochemical cycles. Divers used incubation chambers (domes) on shipwrecks in the southern North Sea where over 55 years mature fouling communities have established. A series of water samples was collected from each dome during deployment to measure the change in concentration of ammonium, nitrite, nitrate, and phosphate. All fauna enclosed in the domes was collected after each measurement for further analysis.

The full macrofauna dataset contained 65 unique species on 4 shipwrecks (25 to 50 species per sample). Abundance ranged from 2187 to 59,427 individuals per sample (683 cm²). On average, a decrease in oxygen concentration of 126 μmol/g ash free dry weight/h was found. The sequential water samples also showed clear changes in nutrient concentration with time in all incubations. The largest changes were observed with high fouling community abundances and biomass. Ammonium, nitrite, and phosphate always increased, with 1.5-to-5-fold increases from start to end of the incubation, while for nitrate both an efflux and influx were measured. Oxygen decreased in all incubations. Mean fluxes (all in μmol per m² per hour with standard error) were significant for ammonium (945 ± 300), nitrite (80 ± 30), phosphate (61 ± 8), and oxygen (−11,794 ± 3289), but not for nitrate (−206 ± 122). Per gram AFDW, only ammonium (12.7 ± 3.5) and oxygen (−126 ± 48) had fluxes that differed significantly from zero.

Compared to average seabed (sandy bottom) oxygen demand and community fluxes from previous studies, the observed fluxes were high. Our findings resembled those from temperate biogenic reef studies. Further data collection across a larger spatial and temporal scale is needed to fully understand offshore structure effects on marine environments.

The effects of oil pollution on nematode assemblages were investigated in a mangrove sediment. Microcosms comprised 350 mL plastic jars filled with 250 g sediment. In the oiled treatments (O), 15 mL oil were added to the soil. In the oil and fertiliser treatments (O + F), oil and fertiliser (N: P: K: 3: 2: 5) were added to the soil. After four weeks, nematodes were extracted and identified. The number of nematode taxa was highest in the C (61), intermediate in the O + F (59) and significantly lower in the O (25) treatment. Taxa present in the C but absent in the O treatment were oil-intolerant. Taxa present in the O treatments were oil-tolerant. Five taxa survived oiling probably due to fertiliser amendment. Oiling eliminated oil-intolerant taxa and favoured those that were resistant. In the O+ F treatment, the number and species of nematodes increased significantly.

In the era of economic globalization and heightened international competition, the emergence of free trade zones has significantly increased regional openness, introducing both new opportunities and challenges for ports. This paper proposes the enhancement of intelligent design in the maritime landscapes of smart ports, with a focus on optimizing internal pathways and developing a predictive model to gauge the impact of smart port landscapes. Furthermore, the study delves into the assessment of risks in smart port supply chains, employing an innovative approach that integrates rough set theory and neural networks. This novel model significantly improves the accuracy of risk evaluation in port supply chains, thereby providing crucial decision support for port management. Additionally, the economic efficiency of smart ports is scrutinized using the Data Envelopment Analysis (DEA) Malmquist index method. Through meticulous selection of research subjects, port efficiency indicators, and the DEA Malmquist index, this analysis offers a comprehensive insight into the economic operations of smart ports. This research not only offers guidance for port economic management but also establishes a framework for the sustainable development of smart ports, thereby ensuring their long-term viability.

The size selectivity and exploitation patterns of two T0 (diamond mesh) codends were tested and compared with T90 (diamond mesh turned by 90°) codends in demersal trawl fishery targeting white croaker (Pennahia argentata) of the northern South China Sea. The four experimental codends involved two mesh sizes, 30 and 35 mm, respectively. The size selectivity of the T0 codend with mesh size of 30 mm, T0_30, was used as a starting point to compare with the rest codends. The results showed that compared with the T0_30 codend increasing the mesh size to 35 mm or applying the T90 codends would result in significantly larger L50 values, and the retention risk (probability) of undersized white croaker with length < 8.5 cm would significantly reduce. These codends, however, had no effect on improving the size selectivity of undersized white croaker with the length ranging between 10 and 15 cm. The results of our study will have relevant implications for fishing gears management and future direction of codend selectivity research.

The vertical structure of internal tidal currents in the Jailolo Strait of the Indonesian seas is studied using the year-long mooring observations with two Acoustic Doppler Current Profiler instruments looking upward and downward, respectively, coving the full depth of the strait. The barotropic tides are extracted from the full-depth current profile measurements, showing the dominant M₂, K₁, and O₁ tidal currents with amplitudes of 13.5 cm s⁻¹, 11.0 cm s⁻¹ and 7.6 cm s⁻¹, in nearly reciprocating movement in the direction of 34.5°, 63.1°, and 75.2° clockwise from due north. The internal tidal currents in the Jailolo Strait contributing to about 50% of the total kinetic energy are found to be dominated by the low baroclinic modes, with M₂ tide as the most dominant tidal constituent. High-frequency internal tides of D₃ and D₄ are observed, with baroclinic structure similar to that of M₂ tides, and are suggested to be stimulated by nonlinear processes. The complicated vertical structure of tidal currents in the Jailolo Strait is disclosed for the first time in history. Its potential impact on vertical turbulent mixing suggests its importance in global ocean circulation and climate.