Metabolic tradeoffs in tropical and subtropical marine mammals - Unique maintenance and locomotion costs in West Indian manatees and Hawaiian monk seals

Unlike the majority of marine mammal species, Hawaiian monk seals (Neomonachus schauinslandi) and West Indian manatees (Trichechus manatus latirostris) reside exclusively in tropical or subtropical waters. Although potentially providing an energetic benefit through reduced maintenance and thermal costs, little is known about the cascading effects that may alter energy expenditure during activity, dive responses, and overall energy budgets for these warm water species. To examine this, we used open-flow respirometry to measure the energy expended during resting and swimming in both species. We found the average resting metabolic rates (RMR) for both the adult monk seal (753.8±26.1 kJ·hr−1, mean±s.e.m) and manatees (887.7±19.5 kJ·hr−1) were lower than predicted for cold water marine mammal species of similar body mass. Despite these relatively low RMRs, both total cost per stroke and total cost of transport (COTTOT) during submerged swimming were similar to predictions for comparably sized marine mammals (adult monk seal: Cost per stroke=5.0±0.2 J·kg−1·stroke−1, COTTOT=1.7±0.1 J·kg−1·m−1; manatees: Cost per stroke=2.0±0.4 J·kg−1·stroke−11, COTTOT=0.87±0.17 J·kg−1·m−1). These lower maintenance costs result in less variability in adjustable metabolic costs that occur during submergence for warm water species. However, these reduced maintenance costs do not appear to confer an advantage in overall energetic costs during activity, potentially limiting the capacity of warm-water species to respond to anthropogenic or environmental threats that require increased energy expenditure.

Vertical distribution of bivalves fauna in the northwestern Tatar Strait (Japan Sea)

General patterns of bivalves distribution by depth in the northwestern Tatar Strait (within Khabarovsk region) are analyzed on the data of 384 trawl, 573 drag, and 1177 diving stations during research surveys in 2003–2016 where the samples were collected with commonly accepted methods. Depths from 0 to 600 m were surveyed. Besides, scientific publications and archival materials related to this area were taken into account. The species richness (y) decreases with depth (x) exponentially from 51 species at 1–20 m to 3 species at 400–600 m that could be approximated satisfactory by the equation y = 31.799. e–0.0502x (r2 = 0.89). Sublittoral and bathial faunas can be separated by cluster analysis of special composition in the depth range 0–150 m and 150–600 m, respectively, with similarity of 0.11 between them. Within these boundaries, 5 local faunas are distinguished: I (< 2 m, the surf zone at the upper boundary of the sublittoral zone), II (2–30 m, the upper sublittoral zone), III (30–150 m, the lower sublittoral zone), IV (150–400 m, the transitional zone) and V (400–600 m, the upper bathyal zone), with similarity between them from 0.14 to 0.36. The upper sublittoral zone has the maximum species richness — 64 species and is the habitat for a «core» of Bivalve fauna with almost ⅔ of its species, preserving the ratio of the main biogeographic groups typical for the researched area. Commercial fishery of scallop Mizuhopecten yessoensis exploited this zone mainly and now is banned to prevent reduction of its stock. Other commercial bivalves, as Callista brevisiphonata, Serripes laperousii, Keenocardium californiense, and Mercenaria stimpsoni, which commercial stocks are estimated in order of 105 t, are also concentrated in this zone but are not landed currently. Portion of moderately cold-water species (wide-boreal and low-boreal) increases and portion of warm-water species (subtropical-boreal and subtropical-low-boreal) decreases with depth, with the slope coefficients of the regressions α = 9.2 ± 4.1 (p = 0.11) and α = –9.6 ± 2.3 (p = 0.03), respectively. The coldwater species are absent in the surf and upper bathyal zones but their portion in other zones is 20–26 %. Rather high portion of boreal-arctic species on shallow depths reflects relative severity of the northwestern Tatar Strait that is the most cold-water area of the Japan Sea. The warm-water species are completely absent in the upper bathyal zone, i.e. at the depths > 400 m. On the other hand, portion of banal species increases and portion of specific species decreases with depth, also portion of rare species increases and portion of mass species decreases with depth, with the slope coefficients α = 9.10 ± 0.49 (p = 0.0003) and α = –4.5 ± 2.5 (p = 0.01), respectively. Vertical distribution of frequent species is rather uniform: 33–57 %. These patterns of the species distribution by zones almost do not change spatially: distribution of different biogeographic groups of species in three coastal areas (47–49о N, 49–51о N, and > 51о N) has no statistically significant differences. Distribution of species richness and composition by depth ranges relates to ecotopic variation (74 % of diversity), to the degree of exploration (22 %), and to the influence of such complex factor as a depth (4 %). Further faunistic studies are recommended in the most diverse areas, as bays, harbours, and capes vicinities with variable grounds and submarine vegetation, in all available depth ranges. Such surveys can provide faunistically representative information on the species wealth. The list of Bivalve mollusk species for the northwestern Tatar Strait can be enlarged possibly in 1/5 if detailed studies of their fauna will be conducted. The fauna on great depths is the most underexplored. The total expected number of bivalve species in this area is at least 120.

The bluefish Pomatomus saltatrix (Pisces: Pomatomidae) in the Adriatic and Tyrrhenian Seas, can we call it climate invader?

Here, we investigate the recent spatio-temporal dynamics of the bluefish Pomatomus saltatrix, a warm water species, which is considered to have conquered the northern Mediterranean coasts due to climate warming. Capitalizing two independent surveys carried out through online questionnaires and vis-à-vis interviews, we accessed the ecological knowledge of 640 recreational fishers, and 206 small-scale fishers, respectively. Respondents provided coherent evidence of a rapid northward expansion of the bluefish along the Tyrrhenian and Adriatic Seas at an estimated speed of 0.8-1.4 degrees of latitude per year. Most fishers in the two seas believed the bluefish to negatively affect both fishing activities and the environment, just as if it was an invasive species and this negative perception was positively correlated with increasing bluefish abundances. The phenomenological effects of this widespread outbreak can be assimilated to a large invasion across various sectors of the Mediterranean Sea, posing the urgency of manage this issue and better understanding its linkage to climate drivers.

Sixteen new generic records of Korean Bryozoa from southern coastal waters and Jeju Island, East China Sea: evidence of tropical affinities

The first records of 16 genera of cheilostome Bryozoa not previously reported for Korea are given here. All are from southern coastal waters, especially Jeju Island, which appears to be Korea’s marine-biodiversity ‘hotspot’. Jodoella koreensis n. gen. et sp. (Robertsonidridae) is new to science. Seven additional new species are described for the genera Copidozoum, Reptadeonella, Schizosmittina, Saevitella, Torquatella, Stephanollona and Plesiocleidochasma. The other genera new to the Korean fauna are Dibunostoma, Corbulella, Onychocella, Stephanotheca, Bryopesanser, Calloporina, Hippaliosina and Pleuromucrum. The Japanese Pleistocene species Calloporina hayamiae Arakawa is newly reported alive from Jeju Island. Four of the species were previously known only from the tropical Indo–West Pacific, three others are found in semitropical/warm-temperate water, and the other known genera have warm-water species, supporting data from other taxa that Korean’s southern waters, especially in the vicinity of Jeju Island, are profoundly influenced by the warm Kuroshio Current and global warming trends. Currently, at least 112 species of Bryozoa are known from Jeju Island, 101 of them Cheilostomata, representing c. 70% of all Korean cheilostome species. Four new combinations are introduced: Copidozoum canui (Sakakura) n. comb., Schizo pedicellata (Soule, Soule & Chaney) n. comb., Torquatella ensenada (Tilbrook) n. comb. and Torquatella longiuscula (Harmer) n. comb. Torquatellidae is subsumed in Celleporidae and Predanophora in Torquatella.

Estimating optimal salinity and temperature of chaetognaths

Determining optimal temperature and salinity for marine organisms is a challenge for marine ecologists because not every species can be easily maintained in the laboratory for testing the influence of environmental parameters. To find a simple method to estimate the optimal temperature and salinity for marine organisms based on survey data, a reciprocal quadratic yield-density model was used for determining the optimal temperature or salinity from abundance data for six pelagic Chaetognatha species. The data for the modelling were collected in four surveys in the East China Sea (23°30′–33°N 118°30′–128°E) from 1997 to 2000. According to both survey data and results from the models, we analysed qualitatively and quantitatively the ecological characteristics of those species. Estimated optimal temperatures and salinities are 17.3°C and 14.1‰ for Sagitta nagae, 20.3°C and 13.8‰ for S. bedoti, 24.9°C and 32.9‰ for S. enflata, 22.5°C and 16.5‰ for S. ferox, 24.5°C and 34.1‰ for S. pacifica and 17.3°C and 14.1‰ for S. pulchra, respectively. Three ecological groups were evident in the East China Sea: the neritic, warm temperate water species (S. nagae); the neritic, warm water species (S. pulchra, S. ferox and S. bedoti); and the oceanic, warm water species (S. enflata and S. pacifica). Our results validate that the model is applicable for describing the relationship between chaetognaths abundance and temperature or salinity.