Changes in Ammonium and pH within Intertidal Sediments in Relation to Temperature and the Occurrence of Non-Indigenous Bivalves

Our objective was to determine the role of two invasive bivalves on the concentration of ammonium as well as pH within intertidal surface sediments (0 - 3 and 3 - 6 cm depth) and interstitial waters, within the context of a warming environment. To meet this objective we applied both controlled laboratory (microcosm) and field (mesocosm) experiments where we varied bivalve presence and absence and sediment temperature. Mesocosm sampling was tide dependent as we attempted to capture changes in ammonium concentration and pH as related to flood and ebb tide. We focused on ammonium as this nutrient is typically a limiting nutrient in oceanic systems and its cycling is a key process that regulates biological productivity. We also determined pH because of the increasing threat of ocean acidification. Integration of laboratory and field studies suggests that bivalves significantly contribute to ammonium to the intertidal with this amount increasing with increasing temperature. This ammonium is then released from the sediment as a “pulse” to overlying seawater on the flood tide. Under laboratory conditions, increased temperature and density of bivalves decreased overlying water pH. Mesocosm studies suggested some tide dependence of pH with flood tide acting as a buffer, increasing pH on the flood tide, after sediment exposure during ebb tide. Increased numbers of invasive bivalves within a warming environment are likely to increase amounts of ammonium released as a pulse on flood tides from intertidal ecosystems making this region a source of ammonium to coastal seas. Greater numbers of non-indigenous bivalves within the intertidal could also contribute to increased acidity within these regions although the significance of such increases is unknown.

Identification of Monitoring Organ in Bivalves for Early Warning of Paralytic Shellfish Toxins Accumulation

Bivalve farming plays a dominant role in mariculture in China.Paralytic shellfish toxins(PSTs)can be accumulated in bivalves and cause poisoning the consumers.A sensitive detection of PSTs can provide early warning to decrease poisoning events in bivalve consuming.PSTs are traditionally examined using the whole soft-tissues.However,PSTs accumulation varies dramatically in different tissues of bivalves.Some tough tissues/organs(such as mantle),which account for a large proportion of the total soft body,exhibit a lower accumulation of PSTs and make the toxin extraction time-and reagent-consuming,potentially decreasing the accuracy and sensitivity of PSTs monitoring in bivalves.To develop a sensitive and cost-effective approach for PSTs examination in massively farmed bivalves,we fed three commercially important bivalves,Yesso scallop Patinopecten yessoensis,Pacific oyster Crassostrea gigas,and blue mussel Mytilus edulis with PSTs-producing dinoflagellate Alexandrium catenella,and detected PSTs concentration in different tissues.For all three bivalve species,the digestive gland accumulated much more PSTs than other tissues,and the digestive gland’s toxicity was significantly correlated with the PSTs toxicity of the whole soft-tissues,with r^(2)=0.94,0.92,and 0.94 for Yesso scallop,Pacific oyster,and blue mussel,respectively.When the toxicity of the whole soft-tissues reached 80μgSTXeq(100g)^(−1),the regulatory limit for commercial shellfish,the digestive gland’s toxicity reached 571.48,498.90,and 859.20μgSTXeq(100g)^(−1) in Yesso scallop,Pacific oyster,and blue mussel,respectively.Our results indicate that digestive gland can be used for the sensitive and cost-effective monitoring of PSTs in bivalves.

Differences in Trace Element Content between Non-Indigenous Farmed and Invasive Bivalve Mollusks of the South African Coast

contents of 23 trace elements (Sc, V, Cr, Mn, Fe, Co, Zn, As, Se, Br, Rb, Sr, Mo, Ag, Sb, I, Ba, La, Ce, Sm, Eu, Hf, Ta) were quantitatively determined in soft tissues and shells of mass non-indigenous bivalve mussels—farmed Pacific oysters (Crassostrea gigas) and farmed and wild invasive Mediterranean mussels (Mytilus galloprovincialis) at the Atlantic coast of South Africa. The study revealed that the contents of the majority of elements in the soft tissues of both species were higher than those in the shells. The tissues of wild invasive Mediterranean mussels contain higher levels of a range of trace elements comparing to farmed mussels. The tissues of Pacific oysters contain much higher levels of almost all elements studied compared to the tissues of Mediterranean mussels. Higher content of zinc in the mussels and oysters from Saldanha Bay may evidence anthropogenic pollution of the bay’s ecosystem by this metal, which necessitates continued monitoring of levels of potentially toxic metals. Both alien species, and especially Pacific oysters, may serve as reliable biomonitors for trace elements in marine ecosystems. Both species are rich in essential elements and provide nutritionally-valuable seafoods.

The Population of the Non-indigenous Bivalve Arcuatula senhousia of the Varano Lagoon (Adriatic Sea,Italy)

A population of the invasive mussel Arcuatula senhousia(Benson in Cantor,1842)was monitored seasonally(May,July and October 2015)in the Varano lagoon,the largest brackish basin of Southern Italy,within the Gargano National Park,Central Adriatic Sea,in order to give information on the abundance,wet weight and frequency classes.The data were collected during a survey carried within the framework of the Regional Project FEP Apulia 2007/2013 “Identificazione di misure per una migliore gestione e conservazione della risorsa vongola nel lago di Varano(FG)”.Summer anoxia may have reduced the mussel population,resulting in less abundance,wet weight and average size in October than in July and May.In particular,about length data,two cohorts were observed in May and October 2015,while a modal distribution in July 2015.

Prey preference of the common long-armed octopus Octopus minor(Cephalopoda: Octopodidae) on three different species of bivalves

Octopus minor is widely distributed along the northern coast of China. To date, there is little information on the prey selection process of this species. To understand this process, several experiments were carried out. Three types of bivalves, namely, Ruditapes philippinarum , Mactra chinensis , and Mytilus galloprovincialis , were used to observe the prey selection of O . minor and to analyze the potential causes of prey selection from three aspects: prey profi tability, adductor muscle tension and handling time. Under single-prey conditions, we found that the average (±SD) predation rates of O . minor on R . philippinarum , M . chinensis , and M . galloprovincialis were 1.73±0.50, 1.27±0.42, and 0.8±0.2/d, respectively. Under diff erent prey combinations, octopods actively selected one type of prey over the other(s), and the order of prey preference was R . philippinarum , followed by M . chinensis and lastly M. galloprovincialis . Furthermore, the shells of the consumed prey showed that O . minor only consumed bivalves by pulling them apart since there was no evidence of drill holes on the shells. The prey selection of O . minor was related to the prey profi tability and handling time;O . minor appeared to select preys with a higher profi tability and a shorter handling time. However, the diffi culty in opening the bivalve was not consistent with the prey preference of the octopods. These results suggest that O . minor prefers to consume R . philippinarum possibly due to a high profi tability and a short handling time that supports the optimum Foraging Theory.

Study on impact of dinoflagellate Alexandrium tamarense on life activities of marine bivalves

The effects of a PSP producing dinoflagellate Alexandrium tamarense on marine bivalvesat their several important life stages: egg, D- shape larva, eyespot larva, juvenile and adult, were studied. The results show that the hatching, survival, activity, filtration and growth were adversely affected by the alga and the impact was significantly increased with the increase of algal density. The inhibitory effect on egg hatching was most significant, which the hatching rate was only 30% of the control when exposed to the alga at 100 cell/cm3 after 36 h. Further experiments show that the algal culture, re-suspended cells and cell fragments had the inhibitory effect, while no such effect was from the cell-free medium, cell contents and standard STX. The results indicate that the alga could produce unknown toxins, rather than PSP, associated with the cell surface.

Health Risk Assessment Due to Heavy Metals Exposure via Consumption of Bivalves Harvested from Marudu Bay, Malaysia

Concern over health risk from consumption of bivalves originating from Marudu Bay is escalating due to the rapid agricultural development surrounding the bay. This has motivated us to estimate the health risk index (HRI) of heavy metals from four commercially important and highly exploited bivalve species which are abundant in the bay. Samples (n = 30) of green mussel (Perna viridis), Asiatic hard clam (Meretrix meretrix), Pacific oyster (Crassosstrea gigas) and marsh clam (Polymesoda expans) were acquired from fishermen in Kg. Teritipan, Marudu Bay. These bivalves were analyzed for heavy metals content using the Inductively Couples Plasma-Optical Emission Spectroscopy (ICP-OES). The study found that the mean contents of Arsenic (As) and Manganese (Mn) in all analyzed bivalves exceeded the permissible limits as well as copper (Cu), lead (Pb) and zinc (Zn) in Pacific oyster, and Zn in marsh clam. It was also noticed that consumption of different bivalve species may bring about health risk from different metals as indicated by varied Total Hazard Index (THI) values. Consumption of the four bivalves was noticed to promote high health risk from As intoxication. Although metal pollution index (MPI) analysis revealed that the bivalves from the bay are currently not seriously impacted by heavy metal pollution, vigorous efforts should be taken to preserve the natural condition of the bay for years to come. There are several ways to minimize health issues from bivalve consumption which include keeping the bivalve natural habitat away from heavy metals pollution by strictly enforcing environmental laws and policies, establishing zones for bivalve fisheries, monitoring heavy metals concentration in bivalve on a regular basis and making depuration process a compulsory requirement in every seafood restaurant throughout the country.

Heavy Metals in Some Fish Species and Bivalves from the Mediterranean Coast of Egypt

Biota samples were collected seasonally during three consecutive years from the Egyptian costal region along the Mediterranean Sea for analysis of Zn, Cu, Cd, Pb and Hg. In addition to bivalve Donax, seven commercially important species of fish were examined to provide a comprehensive assessment for the concentrations of these metals in the Mediterranean coastal region of Egypt. Despite of the presence of several land-based sources of contamination, particularly at El-Mex Bay and El-Maadiya, the results showed very weak increase in the concentration of copper, lead and mercury revealing no accumulation of these metals in the biological material, even in non-migrant bivalve species such as Donax. However, an increase in the concentration of zinc and cadmium in fish tissues was measured from 1993 to 1995. Regardless of the fish species, no significant differences were observed in concentrations of most metals between different locations and from season to season. Regarding concentrations of most metals, no interspecies differences could be also measured in either fish tissues or in bivalve Donax. The study indicated that the concentration of these heavy metals were well below the documented toxic levels for human consumption and represent baseline levels against which possible future heavy-metal contamination can be measured.

Study of Possible Oil Source Rock in Southern Caspian Sea(Iranian Side) with Emphasis on Bivalves and Gastropoda

Most Maikop series,in age of upper-Oligocene to middle Miocene in Republic of Azerbaidjan(western Caspian sea) and Caspian part,is petroleum source rocks.So,considering the interpretation of results gained from correlation between the Maikop series and the Miocene sediments in southern Caspian sea (Iranian side),we suggested that these sediments are probable petroleum source rocks.Recent geochemical studies by Research Center Oil Industry of

Studies on filtration rate in four species of suspension feeding bivalves

The filtration rates of four kinds of bivalves that were cultivated dominantly around Xiamen sea area were measured by using a laboratory flowing system. The experimental results were shown below: (1) Filtration rates were measured in the range of 54 - 74.8 ml/ (g·min) among the four bivalves , sequencing descently Saccostrea cucullata > Sinonovacula constricta > Mytilus viridis > Rudi-tapes philippinarum. (2) The relationship between filtration rates on individual size showed a negative exponential function (FR = aW^b, FR'aW^(b-1), with b - 1 =- 0.435 6 and -0.392. (3) Filtration rates on Skeletonema costatum were much higher than on Alexandrium tamarensis and Scripp-silla trochoidea inS. cucullata and R. philippinarum. (4)FR'on algal densities was also shown a negative function(FR' = aD^(b-1), with b -1 =- 0.143 and -0.215 2 in S.cucullata and R.philippinarum , respectively.

Transverse Variation of Food Compositions of <i>Corbicula bivalves</i>in a Tidal River with Series of Groins

This study was conducted to clarify the food compositions of Corbicula bivalves (C. japonica and leana) in tidal rivers with varied landscapes. In order to grasp their trophic structures, we measured the carbon and nitrogen stable isotope ratios of the collected samples such as the bivalves with varied growth stages and the suspended particulate organic matters (SPOMs) with varied landscapes as their food sources, and then analyzed their relationships with IsoSource mixing model software. The stable isotope ratio measurements clarified that there was a large difference in the ranges of C. japonica and leana in spite of the same sampling locations, and the IsoSource analysis could quantitatively describe their food compositions. According to the results, it could be clarified that the variations in food compositions were dependent not only on the species difference but also on their growth stages. Furthermore, it might suggest that their diet preferences affected the spatial distributions of these Corbicula bivalves in this location.

Species Richness and Abundance of Bivalves and Gastropods in Mangrove Forests of Casiguran, Aurora, Philippines

The diversity and abundance of bivalves and gastropods were studied from April to July 2015. Two sampling stations, Tinib and Esteves, in Casiguran, Aurora were selected based on the presence of mangrove forest, bivalves, gastropods, muddy substrate, and gleaners for the establishment of a transect line. Each station was laid with 100 meters transect line overlaid continuously with 2 m × 2 m quadrat along each transect. A total of 50 sampling units covering 0.02 ha area per sampling station were surveyed. The transect line recorded six species of bivalves distributed among five families and 12 species of gastropods belonging to eight families. Three species of bivalves and five species of gastropods were common to both sampling stations. However, Tinib station had most diverse species of bivalves (0.55) while Esteves station had most diverse species of gastropods (0.43). Both stations revealed Dendrostrea folium (43%) (bivalve) and Cerithidea cingulata (93%) (gastropods) as most frequently occurring species. Dendostrea folium also emerged as the densest (10,640 ind∙ha−1 and 6850 ind∙ha−1) and most abundant (58.52% and 77.84%) bivalve species. For gastropods, Terebralia sulcata (249,250 ind∙ha−1) was the densest and most abundant (96.97%) in Tinib while Terebralia palustris was the densest (747,050 ind∙ha−1) and most abundant (70.44%) in Esteves. Pooled results for bivalve species maintained Dendrostrea folium as the densest (8750 ind∙ha−1) and most abundant (64.81%). However, for gastropods, Terebralia palustris emerged as the densest (373,525 ind∙ha−1) and most abundant (56.70%) species. The mangrove forests of Casiguran, Aurora thus contain a variety of bivalves and gastropods with Tinib station dominated by bivalves while Esteves station dominated by gastropods.

Hauterivian-Barremian Bivalves from the Boulouha Formation of the Dahar Escarpment, Southern Tunisia: Stratigraphy and Regional Correlation

The Lower Cretaceous mixed siliciclastic-carbonate successions of the Boulouha Formation at the type locality in the Dahar escarpment of southern Tunisia have yielded a new discovered assemblage of bivalves which contains Anomia laevigata (Sowerby);Modiolus sp. cf. M. dahuashuensis (Yu et Li);Astarte sp.;and ?Mytilus sp.. The temporal distribution of the Anomia laevigata (Sowerby) and Modiolus sp. cf. M. dahuashuensis (Yu et Li) is limited to the Aptian formations of northeastern China, Japan and Korea, thus we suggest a Hauterivian-Barremian age for the Boulouha Formation. Henceforth, the new biostratigraphic data are used to improve a regional chronostratigraphic correlation between the lower Cretaceous strata of the Saharan Platform domain and those coeval from the Chotts domain.

Spatial Zonation and Diversity of Bivalves and Gastropods in Mangrove Forests of Casiguran, Aurora, Philippines

This study generally aimed to determine the spatial zonation and diversity of bivalves and gastropods in mangrove forest of Cozo, Esteves and Tinib in Casiguran, Aurora. Specifically, this aimed to determine the species composition and distribution, and determine the relationship between spatial zonation and diversity of bivalves and gastropods as influenced by ecological factors such as vegetation, soil texture, organic matter, soil salinity, and soil pH. A total of 22 taxa comprising eight species of bivalves and 14 species of gastropods were identified. The high tidal zone of Esteves had high diversity (0.66) of bivalve species compared to other tidal zones and areas. On the other hand, the diversity of gastropods was almost equal in the middle tidal zones of Cozo (0.60), Esteves (0.57), and Tinib (0.42). In terms of bivalve species’ density and abundance, Dendostrea folium was the most dense and abundant in the low tidal zone of Cozo (253,333 ind.ha−1 or 25 ind.m2-1, 97.44%) while Gafrarium tumidum in the low tidal zones of Esteves (46,666 ind.ha−1 or 4 ind.m2-1, 73.68%) and Tinib (126,666 ind.ha−1 or 12 ind.m2-1, 50%). In terms of gastropod species’ density and abundance, Cerithidea cingulata was the most dense and abundant in the low tidal zone (666,666 ind.ha−1 or 66 ind.m2-1, 65.79%) of Cozo and the middle tidal zone (5,280,000 ind.ha−1 or 528 ind.m2-1, 61.40%) of Tinib. It was Terebralia palustris in the low tidal zone (1,263,333 ind.ha−1 or 126 ind.m2-1, 63.06%) of Esteves. All tidal zones within each study area had greater dissimilarities in terms of bivalves but had greater similarities in terms of gastropod species’ compositions. On the other hand, all tidal zones between study areas had greater dissimilarities in terms of bivalve and gastropod species present. Most tidal zones had Gafrarium tumidum as common bivalve species while Neritidae sp. and Cerithidea cingulata were common gastropod species. All these species were found thriving in a wide range of vegetation, soil texture, organic matter, soil salinity and pH.

Treatment of Shrimp Effluent by Integrated Culture of Bivalves and Macroalgae

[Objectives]To provide a theoretical basis for constructing the best species suitable for local shrimp-bivalves-algae IMTA through the screening of different bivalves and the determination of seaweed density.[Methods]The preliminary studies of different kind of bivalves and macroalgae(Gracilaria lichevoides)used for the purification of shrimp effluent were described.Through the screening of benthic bivalves,the best ratio of integrated culture of bivalves and algae was determined.[Results]Both bivalves and macroalgae had certain purification effects on aquaculture wastewater,but the effects significantly differed from species and breeding density.The removal rate of nutrient declined from Potamocorbula laevis,Sinonovacula constricta,Tegillarca granosa.The mixotrophic culture of 8 ind/L P.laevis and 120 g G.lichevoides had the highest efficiency of purification and removal rates of nutrient:NH4-N:90.67%,TP:86.18%,TN:72.66%,NO3-N:51.85%,respectively.There was a significant difference between the blank control group and the other three groups(P<0.01).The 8 ind/L+120 g group was significantly higher than the 4 ind/L+120 g group(P<0.05)in TP removal rate.Additionally,the difference between four groups was significant in the removal rate of NH4-N and TN(P<0.05),but 2 ind/L+120 g group and 8 ind/L+120 g group in the removal rate of NO3-N had no significant difference(P>0.05).[Conclusions]This research provides a reference for the use of filterable shellfish and large seaweed to treat aquaculture wastewater,and also provides the theoretical basis for constructing the local multi-level breeding structure.

Study of some marine bivalves as the biomonitor candidates for environmental assessment of the Jiaozhou Bay by NAA and AAS

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Verify the Function of a Potential Growth-Regulating Gene in Marine Bivalve Using a Candidate Model Organism Mulinia lateralis

A better understanding of genetic bases of growth regulation is essential for bivalve breeding,which is helpful to improve the yield of the commercially important bivalves.While previous studies have identified some candidate genes accounting for variation in growth-related traits through genotype-phenotype association analyses,seldom of them have verified the functions of these putative,growth-related genes beyond the genomic level due to the difficulty of culturing commercial bivalves under laboratory conditions.Fortunately,dwarf surf clam Mulinia lateralis can serve as a model organism for studying marine bivalves given its short generation time,the feasibility of being grown under experimental conditions and the availability of genetic and biological information.Using dwarf surf clam as a model bivalve,we characterize E2F3,a gene that has been found to account for variation in growth in scallops by a previous genome-wide association study,and verify its function in growth regulation through RNA interference(RNAi)experiments.For the first time,E2F3 in dwarf surf clam,which is termed as MulE2F3,is characterized.The results reveal that dwarf surf clams with MulE2F3 knocked down exhibit a reduction in both shell size and soft-tissue weight,indicating the functions of MulE2F3 in positively regulating bivalve growth.More importantly,we demonstrate how dwarf surf clam can be used as a model organism to investigate gene functions in commercial bivalves,shedding light on genetic causes for variation in growth to enhance the efficiency of bivalve farming.