The genus Centrodinium contains oceanic and predominantly tropical species that have received little attention. Three species of Centrodinium were examined using thecal plate dissociation, scanning electron microscopy, and molecular sequences. The apical horn of Centrodinium intermedium and C. eminens is formed by the elongation of the fourth apical plate, and a second apical split into two plates. In C. punctatum two apical plates (2&#x2032; and 4&#x2032;) almost completely encircle the apical pore plate (Po), while the contact with the plate 1&#x2032; in the ventral side is much reduced, and the plate 3&#x2032; does not reach the Po. Moreover, its left posterior lateral sulcal plate is longer than its right pair, while reversed in the typical Centrodinium spp. The sulcal posterior plate of C. punctatum is located in the left-ventral side below the plates 1&#x2032;&#x2032;&#x2032; and 2&#x2032;&#x2032;&#x2032;, while the sulcal posterior plate located in the right face below the plates 4&#x2032;&#x2032;&#x2032; and 5&#x2032;&#x2032;&#x2032; in the typical Centrodinium spp. Phylogenetic analyses based on the small and large subunit of the rRNA gene showed that Centrodinium spp. and Alexandrium affine/A. gaarderae clustered as a sister clade of the Alexandrium tamarense/catenella/fraterculus groups. The clade of the subgenus Gessnerium, and the clade of the type species of Alexandrium, A. minutum, with four divergent species, clustered in more basal positions. The polyphyly of Alexandrium is solved with the split into four genera: (1) Alexandrium sensu stricto for the species of the clade of A. minutum and four divergent species; (2) the reinstatement of the genus Gessnerium for the species of the clade of A. monilatum; (3) the reinstatement of genus Protogonyaulax for the species of the tamarense/catenella/fraterculus groups, and (4) the new genus Episemicolon gen. nov. for A. affine and A. gaarderae. New combinations in the genera Gessnerium, Protogonyaulax, and Episemicolon are proposed.

Fernando G&#x00F3;mez

Luis Felipe Artigas

Redefinition of the Dinoflagellate Genus Alexandrium Based on Centrodinium: Reinstatement of Gessnerium and Protogonyaulax, and Episemicolon gen. nov. (Gonyaulacales, Dinophyceae)

Hypnea bryoides collected from the Arabian Sea on the southern coast of Oman was investigated for &#x3ba;-carrageenan optimal extraction conditions. The effects of different conditions of alkali treatment (4, 6, and 8&#x25; w/v NaOH), temperatures (70, 75, and 80&#xb0;C), and time (2, 2.75, 3.5 hours) on carrageenan yield and chemical and thermal properties were evaluated. Yield was significantly affected by alkaline concentration and temperature, with highest value of 26.74 &#xb1; 5.01&#x25;. Molecular weights of the extracted carrageenan were significantly reduced by increased temperatures and ranged from 5.95 &#xb1; 0.49 &#xd7; 105&#x2009;Da to 13.90 &#xb1; 0.14 &#xd7; 105. FTIR showed that samples under all extraction conditions were similar and confirmed the presence of &#x3ba;-carrageenan with no traces of &#x3bc;-precursor. Sulfate content was also significantly reduced by alkaline concentration (from 4&#x25; to 6&#x25;) and ranged from 7.62 &#xb1; 5.52&#x25; to 17.02 &#xb1; 0.14. Thermal properties showed more sensitivity towards temperature and alkaline strength parameter than time. In addition, melting and gelling temperatures were significantly correlated with the molecular weight, but not sulfate content. In conclusion, mild extraction conditions were found to be more efficient in introducing the intended structural modification while getting the highest yield and quality.

Zainab Mohammed Al-Nahdi

Ahmed Al-Alawi

Insaaf Al-Marhobi

The Effect of Extraction Conditions on Chemical and Thermal Characteristics of Kappa-Carrageenan Extracted from Hypnea bryoides

In the exploration of the hydrothermal system of the Guaymas Basin (GB) between 27&#xb0; 00&#x2032; 35&#x2032;&#x2032; and 27&#xb0; 00&#x2032; 50&#x2032;&#x2032; N and 111&#xb0; 24&#x2032; 15&#x2032;&#x2032; and 111&#xb0; 24&#x2032; 40&#x2032;&#x2032; W in the Gulf of California, carried out on the R/V Atlantis and of the DSRV/Alvin in October 2008, four cores of surface sediments were obtained to analyse photosynthetic pigments at two locations with contrasting extreme conditions: Oil Town and Great Pagoda. We identified nine pigments: Chlorophyll-a, Phaeophytin-a, Phaeophorbide-a, Pyropheophytin-a (degradation Chlorophyll-a products), &#x3b2;-Carotene, Alloxanthin, Zeaxanthin, Diadinoxanthin, and Prasinoxanthin (carotenoids). The maximum pigment concentration was registered in the Great Pagoda (10,309 ng/g) and the minimum in Oil Town (918 ng/g). It is demonstrated that photosynthetic pigment profiles in surface sediments depend on the heterogeneity of the extreme conditions of each site caused mainly by temperature and bacterial substrates. Therefore, there were significant differences (p &#x3c;0.05) in the pigmentary profile of the four sedimentary cores analyzed. However, no statistical differences (p &#x3e; 0.05) in the concentration of pigments have been detected. We conclude that the photosynthetic pigments contained in the surface sediments of the hydrothermal vents in the Guaymas Basin are primarily of chemoautotrophic bacterial origin.

D. B. Ram&#xed;rez-Ortega

L. A. Soto

A. Estradas-Romero

F. E. Hern&#xe1;ndez-Sandoval

Photosynthetic Pigments Contained in Surface Sediments from the Hydrothermal System of Guaymas Basin, Gulf of California

The trends of the world&#x2019;s top ten countries relating to shark bite rates, defined as the ratio of the annual number of shark bites of a country and its resident human population, were analyzed for the period 2000-2016. A nonparametric permutation-based methodology was used to determine whether the slope of the regression line of a country remained constant over time or whether so-called joinpoints, a core feature of the statistical software Joinpoint, occurred, at which the slope changes and a better fit could be obtained by applying a straight-line model. More than 90&#x25; of all shark bite incidents occurred along the US, Australia, South Africa, and New Zealand coasts. Since three of these coasts showed a negative trend when transformed into bite rates, the overall global trend is decreasing. Potential reasons for this decrease in shark bite rates&#x2014;besides an increase in the world&#x2019;s human population, resulting in more beach going people, and a decrease of sharks due to overfishing&#x2014;are discussed.

Erich Ritter

Raid Amin

Kevin Cahn

Jonathan Lee

Against Common Assumptions, the World&#x2019;s Shark Bite Rates Are Decreasing

The concept of &#x201c;sustainability&#x201d; has become the current answer to absolving the world of its environmental and economic crises in the 21st century. This paper analyses seven socioeconomic factors (age of household head, household average annual income, marital status of household head, gender of household head, household size, education level of household head, and period of residence of household head) influencing extreme degradation of seagrass and exploitation of mangrove resources in Zanzibar, Tanzania. To accomplish this, Participatory Rural Appraisal approaches and household questionnaire survey were used to obtain information on primary data. Multiple regression analysis and descriptive statistics were used to analyze quantitative data while content analysis was used to analyse qualitative data. The findings revealed that all the socioeconomic variables tested were statistically significant (P&#x3c;0.05) and had an influence on the exploitation of mangrove and degradation of seagrass except gender of the household (P=0.88) and household annual average income (P=0.655), respectively. In addition, statistical analysis revealed that there was significant difference in the mangrove status between the sites (p= 0.0001, &#x3c7;2 =27.27) with more exploitation at Charawe compared to Kibele village, whereas no significant differences were revealed in the status of seagrass between the two sites (p= 0.2693, &#x3c7;2 =1.2202). On one hand, the findings revealed that at Kibele and Charawe 60&#x25; and 50&#x25; practice gleaning, 40&#x25; and 55&#x25; are engaged in seaweed farming, and 60&#x25; and 70&#x25; collect bait from seagrass meadows, respectively. All these activities had direct influence on seagrass status. On the other hand, the finding revealed that livelihood needs, population growth, level of education, and lack of alternative source of income are the key drivers to exploitation of coastal natural resources especially mangrove and seagrasses. To ensure sustainable exploitation of coastal resources alternative livelihood activities such as farmed fish, small/petty business, and agriculture activities that are profitable and easy to manage should be introduced to the local coastal community to enhance active participation in conserving resources and improving their livelihood.

Amina A. Nchimbi

Liberatus D. Lyimo

Socioeconomic Determinants of Mangrove Exploitation and Seagrass Degradation in Zanzibar: Implications for Sustainable Development

Sea cucumbers can mitigate some impacts of climate change through digestion of benthic sands and production of calcium carbonate. The projected ecological benefits of sea cucumbers in warmer, more acidic oceans are contingent on the capacities of individuals to acclimate and populations to adapt to climatic changes. The goal of this experiment was to evaluate the degree to which warming waters would impact three abundant species of sea cucumbers on the Heron Reef in Queensland, Australia. We conducted a behavioral assay using three species of sea cucumbers, Holothuria atra, Stichopus chloronotus, and Holothuria edulis. Individuals from each species were subjected to three conditions mimicking current summer temperatures, current winter temperatures, and an elevated temperature consistent with future ocean warming by the year 2100. Sea cucumber reactions were evaluated using righting time as a proxy for their stress levels and overall tolerance of warming events. The three sea cucumber species reacted differently to water temperature changes: H. atra&#x2019;s righting times declined with temperature, S. chloronotus had greater righting times at high and low temperature extremes, and H. edulis&#x2019;s righting times remained relatively constant throughout. Our results suggest that each of these species might respond differently to ocean warming and while some may be able to continue to combat climate change in benthic communities, others may decline in ecological function.

Elizabeth Buccheri

Matthias W. Foellmer

Beth A. Christensen

Paul Langis

Stefani Ritter

Esther Wolf

Aaren S. Freeman

Variation in Righting Times of Holothuria atra, Stichopus chloronotus, and Holothuria edulis in Response to Increased Seawater Temperatures on Heron Reef in the Southern GBR

Species of the genus Ulva are common in anthropogenically disturbed areas and have been reported as the cause of green tides in many areas of the world. In addition, they rank among the main marine groups used in a wide range of commercial applications. By displaying few distinctive morphological characters, some taxonomical identifications are difficult and the genus is under a conundrum. Our aims were to provide ecophysiological information about three Ulva species in response to abiotic factors and to evaluate the proposal of ecophysiological information and the chlorophyll-a fluorescence technique as auxiliary tool to resolve the long-standing taxonomic confusion. We hypothesize that three cooccurring specimens (U. fasciata Delile, U. lactuca Linnaeus, and U. rigida C. Agardh) have different ecophysiological responses (as measured by the effective quantum yield of photosystem II by pulse amplitude modulated fluorometers) under manipulated conditions of temperature and nutrient concentration. Ulva lactuca and U. rigida showed different photosynthetic efficiencies related to temperature, whereas no difference was recorded for U. fasciata individuals. These results provide a reasonable explanation for the variability in spatial and temporal abundance of these species of Ulva on rocky shores. We proposed the use of ecophysiological information by chlorophyll-a fluorescence as an auxiliary tool to corroborate the taxonomic distinction of Ulva species. We reinforce the statement of U. fasciata and U. lactuca as distinct valid species.

Vin&#xed;cius Peruzzi Oliveira

Barbara Lage Ignacio

Nuno Tavares Martins

Leticia Dobler

Alex Enrich-Prast

The Ulva spp. Conundrum: What Does the Ecophysiology of Southern Atlantic Specimens Tell Us?

Marine organisms are exposed to a pH decrease and to alteration of carbonate chemistry due to ocean acidification (OA) that can represent a source of oxidative stress which can significantly affect their antioxidant defence systems efficiency. The polychaetes Platynereis dumerilii and P. massiliensis (Nereididae) are key species of the benthic community to investigate the effect of OA due to their physiological and ecological characteristics that enable them to persist even in naturally acidified CO2 vent systems. Previous studies have documented the ability of these species to adapt to OA after short- and long-term translocation experiments, but no one has ever evaluated the basal antioxidant system efficiency comparing populations permanently living in habitat characterized by different pH conditions (acidified vs. control). Here, individuals of both Platynereis species, sampled from a natural CO2 vent system and from a nonventing &#x201c;control&#x201d; site in three different periods (April 2016, October 2016, and February 2017), were compared highlighting signals which suggested the ability of both species to acclimatize to high pCO2&#x2013;low pH with slight seasonal variations of their antioxidant efficiency and the absence of disturbances of the oxidative status of Platynereis spp. tissues.

Giulia Valvassori

Maura Benedetti

Francesco Regoli

Maria Cristina Gambi

Antioxidant Efficiency of<italic> Platynereis</italic> spp. (Annelida, Nereididae) under Different pH Conditions at a <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" style="vertical-align:-3.18147pt" height="11.8239pt" version="1.1" viewBox="-0.0498162 -8.64243 24.0698 11.8239" width="24.0698pt"><g transform="matrix(.013,0,0,-0.013,0,0)"><path id="g187-68" d="M625 186C574 85 512 32 429 32C293 32 194 153 194 337C194 485 274 621 419 621C496 621 573 586 606 468L643 475C636 537 629 583 620 638C593 644 519 665 438 665C199 665 42 523 42 317C42 158 152 -15 418 -15C486 -15 578 5 604 11C621 46 647 122 660 171L625 186Z" /></g><g transform="matrix(.013,0,0,-0.013,8.932,0)"><path id="g187-80" d="M394 664C165 664 42 495 42 323C42 132 181 -15 381 -15C570 -15 725 116 725 332C725 529 576 664 394 664ZM374 622C491 622 571 503 571 304C571 120 494 27 399 27C271 27 196 171 196 343C196 516 274 622 374 622Z" /></g><g transform="matrix(.0091,0,0,-0.0091,18.96,3.132)"><path id="g187-243" d="M442 172C405 109 393 108 333 108H171L289 222C383 315 430 374 430 457C430 569 349 635 249 635C187 635 134 610 97 573L34 478L61 455C93 502 136 542 196 542C265 542 300 491 300 422C300 346 261 273 191 190C142 132 84 76 31 25V0H432C443 42 455 105 471 163L442 172Z" /></g></svg> Vent&#x2019;s System

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Journal of Marine Sciences publishes original research articles as well as review articles&nbsp;in all areas of marine sciences including marine biology, oceanography, hydrology, coastal processes, technological developments, climate change, and policy.

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Journal of Marine Sciences publishes original research articles as well as review articles in all areas of marine sciences including marine biology, oceanography, hydrology, coastal processes, technological developments, climate change, and policy.

Journal of Marine Sciences