Seabed scour caused by propellers is an increasingly widespread issue with respect to offshore developments as a result of the continually rising sizes of vessels. This literature review aggregates current research literature from 2020 through 2025 with respect to hydrodynamic principles of propeller jets, seabed scouring, computational fluid dynamic models of scouring, and related coastal engineering principles. Major research findings buttress the importance of jetting confinement factors, sediments, and transient conditions of vessel operation. Although research progress in computational fluid dynamic models of seabed scouring from Reynolds averaged Navier Stokes models to more complex models has been beneficial, major research gaps must be filled in models of seabed scouring on cohesive sediments, more representative models of maneuvering conditions, and valid comparisons with real-world data. Major research areas that need to be emphasized in the not too distant research future must encompass research on dynamic principles of seabed sediments, real-world hydrodynamic principles of vessels, data gathering for real-world applications, and engineering models of enhancing seabed scouring resilience.

The restoration of European flat oyster (Ostrea edulis) population is critical for biodiversity and ecosystem services recovery. This study evaluates the potential of innovative clay substrates, developed and patented by Oyster Heaven, as cost-effective and degradable alternatives for large-scale oyster reef restoration. Field trials conducted in an oyster aquaculture site and hatchery experiments under controlled conditions assessed the larvae settlement efficiency, microbial biofilm composition, and environmental influences. Results showed significantly lower larvae recruitment on clay prototypes and spat collectors used as control, in wild conditions, with environmental factors such as temperature and hypoxia playing a key role. In the hatchery, larvae preferred oyster shells (17,174 ± 659 spats/m2) over clay prototypes (2917 ± 111 spats/m2) and spat collectors (1451 ± 160 spats/m2). Microbial analysis revealed a shift towards Cyanobacteria and Woeseia species, with Pseudoalteromonadaceae, a genus previously linked to both stimulating and inhibiting larvae settlement, detected only on clay surfaces. Despite challenges, the clay prototypes demonstrated potential as sustainable substrates for restoration, particularly in managed “spats-on-reefs” strategies. This research highlights the importance of environmental monitoring, microbial interactions, and substrate optimization in enhancing restoration success for O. edulis populations. Further investigations are recommended to refine clay designs and assess their broader applicability under variable environmental conditions.

The cytological characteristics of major green-tide-forming green algae Ulva prolifera collected from Yellow Sea were studied through cutting segments, long time low temperature or dark treatments. After being dried in the shade and preserved at -20°C for 30 days, the U. prolifera was cultured at 4°C in sterilized seawater under 40 μmol photons m-2·s-1 light intensity for 120 days, results indicated that the plastid of U. prolifera continuously shrank with the extension of treatment, and most cells turned white and died, only a small amount of cells still contained a few of visible inclusions at the 120d of treatment. Then those samples were transferred to 20°C and 40 μmol photons m-2·s-1 condition for recovery cultivation, after about 10 days, some recovery cells were observed in the thallus, and those cells developed to young thallus gradually and released germ cells almost in the same time. After about 60 days of recovery cultivation, the newly-grown green thallus broke through the original dead thallus, and the germ cells also grew to new individual thallus. Before dark treatment, the U. prolifera cells were filled with plastid, contained visible starch grain and discernible cell outlines, while after 120 days of dark treatment, the plastid shrank and degraded together with the disappearance of cell inclusions, and the cell outlines also blurred, then those samples were transferred to optimal culture conditions at 20°C in 40 μmol photons m-2·s-1 light intensity, and 15 days later, newly-grown cells appeared on the almost dead thallus, these cells divided continuously and grew to young thallus, and those newly-grown thallus also generated active germ cells, which developed to new thallus that cytologically identical to the original thallus. Observation of chopped tissue of U. prolifera cultivated at 20°C, 40 μmol m-2·s-1 showed that the morphological upper part cells turned to germ cells first, those germ cells including gametophyte and sporophyte, which released later and grew to new individual thallus. These findings provided cytological evidences for how U. prolifera live through stress conditions such as low temperature, darkness, and also useful for understanding the mechanism of the occurrence of green tide.

An analysis of the variation of the density and biomass of the fish communities of the lagoon of La Paz, Mexico was carried out from November 2016 to September 2017. A total of 2763 organisms were collected with a total biomass of 211,422.93 g in an area of 5022 m2, a density and biomass of 0.550 lnd/m2 and 44.091 g/m2. The site with the largest biomass was recorded in Zacatecas (11.179 g/m2) located north of the lagoon, while Grand Plaza recorded the lowest biomass (2.732 g/m2). Regarding the density, the maximum value was recorded in the site Yate Hundido, located northwest of the lagoon (0.129 lnd/m2) and the lowest was Las Palmas (0.036 lnd/m2) located north of the lagoon. The most abundant species was Diapterus peruvianus with 683 individuals and a biomass of 37,507.57 g. The physicochemical variables showed two seasons with significant change where we can observe higher temperatures in the summer (average of 27.45°C) and minimum in winter (average of 22.49°C). The Shannon-Weaver diversity index showed a difference (p = 0.050) between months, with the highest value recorded in April (H' = 2.133 bits/ind) and the lowest in June (H' = 1.041 bits/ind). The biomass and density values recorded in the lagoon were found to be associated with the spatio-temporal variation of temperature of the lagoon, as well as the resident and transitory species located in the area of study. In addition, the body sizes recorded corresponded to juvenile and young adult individuals.

The decline in herbivorous fishes is an important contributing factor to the degradation of coral reefs, because their reduction contributes to macro algae overgrowth, which can have harmful effects on corals. Herbivorous fish often form mixed-species groups to locate foraging sites and for defense. The movements and compositions of these groups are dependent on the relative numbers of different species present. Some species, such as the striped parrotfish (Scarus iserti) and ocean surgeonfish (Acanthurus bahianus), serve as core species that lead mixed-species groups. Others, such as the redband (Sparisoma aurofrenatum) and stoplight parrotfishes (Sparisoma viride), follow core species as their associates. Despite the potential importance and abundance of mixed-species groups on reefs, little attention has been given to their composition and movements. Our intent was to determine whether the social dynamics of mixed-species groups in Jamaica were similar to those of Grand Cayman. The overall sizes of mixed-species groups were smaller in Grand Cayman. Focal striped parrotfish in Grand Cayman formed smaller groups, changed composition less, and moved less frequently than in Jamaica. Although probably more abundant than striped parrotfish, the ocean surgeonfish in Grand Cayman did not function as a core species but rather attached themselves as associates to the smaller striped parrotfish groups. Redband parrotfish moved less often in Grand Cayman, and appeared to be more dependent on striped parrotfish groups than stoplight parrotfish. While previous studies on herbivorous reef fish have shown that changes in foraging patterns can change with location, perhaps related to structural heterogeneity and resource distribution, this study illustrates that social interactions between common members of mixed-species groups also change. We suggest that the intra and interspecific social interactions in Grand Cayman are less attuned to finding erratically located high quality resources than those in Jamaica. Other plausible explanations are also considered.

An ecological zonation of phytoplankton was determined from its normalized spectral absorption shape (aphn) during the summers of 2001-02-03 off the west coast of Baja California. In the first two seasons, the highest abundances of the main taxonomic groups of phytoplankton were detected towards the coastal stations, but for 2003, diatoms showed higher abundances towards the oceanic region. The ecological provinces (Pv) were the footprint of the zonation in the structure of the phytoplankton community; likewise, it was observed that the spectral shape was independent of the chlorophyll-a (mg·m-3). The effect of coastal upwelling south of Vizcaíno Bay favored the increase of phytoplankton cells. However, the composition of the community decreased in cells abundance and diversity due to the influence of the phenomenon called El Nino “débil” reported to the south of the California Current for the years 2002-03.

The maritime industry is currently facing the challenges of adopting new technologies and operational practices with stricter international, national and local rules in order to reduce exhaust gas emissions from ships. The most objective of regulations introduced and presented by the Worldwide Sea Organization such as International Maritime Organization (IMO) and the US Environmental Protection Agency (EPA) is to lessen the commitment shipping makes to worldwide and local discharges. This paper analyzes emissions from marine engines and the process of waste exhaust gas formation and provides a summary of the emission reduction technologies to satisfy MARPOL NOx tier III and EPA tier IV rules. The results showed the possibility of achieving a valuable emission reduction percentage if future diesel engines are equipped with pre-treatment, internal-treatment and/or post-treatment techniques. Economics impact for medium and low speed for category 3 marine diesel engines is also presented.

The island of Jamaica is often cited as an example of how overfishing has dramatically reduced the sizes of coral reef fishes. To examine the change in fish sizes over a 36-year period, we analyzed data from systematic surveys conducted in 1977 and 2013/14 of the sizes and relative abundances of four common algae-grazing fishes in the shallow backreef habitats of Jamaica and Grand Cayman. The four species are: striped parrotfish (Scarus iseri), stoplight parrotfish (Sparisoma viride), ocean surgeon (Acanthurus tractus) and the blue tang (Acanthurus coeruleus). We predicted that all four species would be larger in Grand Cayman than in Jamaica in 1977 as well as in 2013/14, because Grand Cayman has been cited as having less fishing pressure than Jamaica. For the same reason, we expected all four species would have declined in size over the 36 years in Jamaica but not in Grand Cayman. Furthermore, we predicted that the compressed body shape of the ocean surgeon and the blue tang would have made them especially vulnerable to net and trap fishing compared to the two parrotfishes, and that accordingly the effects of overfishing would be greater in these two species. We rejected this hypothesis. The size distributions of the laterally compressed species changed significantly on both islands over the 36-year time span, although not as predicted. At both islands, the blue tangs shifted toward smaller sizes and the ocean surgeons shifted toward larger sizes. There were no size distribution changes detected in the two fusiform species. There was also no support for the prediction that the sizes of these four species were larger in Grand Cayman than in Jamaica during either time period.

Blue mussels, Mytilus edulis , form dense beds of both commercial and ecological importance, and many attempts have been made to determine their filtration rate. The total time in which mussels actually utilise their filtration capacity in nature varies greatly, making in situ methods for filtration rate measurements relevant. Further, it is being debated to what extend filtration rates measured in the laboratory using cultivated algal cells may apply for mussels in nature. In the present study, we have used an open-top chamber setup in order to allow repeated in situ filtration rate measurements of M. edulis using ambient natural phytoplankton and free-living bacteria. We found that the in situ measured filtration rates are comparable to filtration rates obtained in laboratory studies using different methods and controlled diets of cultivated algal cells. Further, we found that the retention efficiency of free-living bacteria was between 22.2% and 29.9%, in good agreement with values from laboratory studies. Our findings support the assumption that mussels in nature tend to use their filtration capacity when the phytoplankton concentration is above a certain lower trigger level.