Northeastern Persian Gulf Research Articles

Dynamics of Dipsastraea pallida-symbiont association following bleaching events across the northern Persian Gulf and Gulf of Oman

Reef-building corals are in obligate symbiosis with dinoflagellates of the family Symbiodiniaceae. The partnership, however, is prone to breakdown as a result of thermal stress, which leads to coral bleaching. According to the Adaptive Bleaching Hypothesis, corals’ recovery from bleaching is profoundly influenced by forming stable associations with thermotolerant algal strains during bleaching. Consequently, the knowledge of the diversity of host-symbiont associations during this period is substantial. Since the extent of symbiont shuffling varies among different host taxa, we investigated the diversity of dominant Symbiodiniaceae in association with the scleractinian coral Dipsastraea pallida before and after massive bleaching events of 2017 in the Persian Gulf and 2018 in the Gulf of Oman. We observed a flexible association between D. pallida and five lineages of Symbiodiniaceae (i.e., ITS2-types A1.4, C3, C39, D1a, D5) with a clear regional pattern. However, the pattern of these associations was changed following bleaching events, with the complete replacement of Cladocopium-C39 by Durusdinium-D1a in the Gulf of Oman, and increased proportion of Durusdinium-D1a and disappearance of Symbiodinium-A1.4 in the northeastern Persian Gulf. In the westernmost Persian Gulf, on the other hand, a stable D. pallida-Cladocopium-C3 partnership was observed. These findings convey the potential of D. pallida to shift the prevalence of its symbiont communities within a population in response to bleaching, which may reflect symbiont shuffling and/or differential mortality and partly explain the predominance of Dipsastraea corals in the Persian Gulf and Gulf of Oman.

The enhanced expression of heat stress-related genes in scleractinian coral ‘Porites harrisoni’ during warm episodes as an intrinsic mechanism for adaptation in ‘the Persian Gulf’

Shallow water tropical reefs are widely threatened by anthropogenic ocean warming which sometimes exceeds their thermal tolerance limit. The majority of reefs have been currently predicted to entirely disappear if CO2 emissions continue at the present rate. However, certain species are thermally resilient and can quickly adapt to anomalous thermal stress events by altering the expression of heat stress-related genes, known as gene expression plasticity. Here, we examined the expression of key genes (i.e., heat-shock proteins, oxidative stress, immune response, ion transport, apoptosis, anti-apoptosis) in the scleractinian submassive coral Porites harrisoni and cytochrome P450 gene of its algal symbionts collected from the northeastern Persian Gulf during warm (August) and cold (December) periods. The potential for recovery from severe heat stress in August was additionally examined through transplantation of partially bleached coral fragments from shallow (~ 2.5 m) to a deeper site (~ 9 m), close to colonies of the same species experiencing much less heat stress. To evaluate the acclimation capability, several healthy deep (~ 9 m) coral fragments were transplanted to the shallow (~ 2.5 m) site experiencing severe heat stress. A significant upregulation of heat-shock proteins in response to heat stress was found and identified as the primary defense mechanism against heat stress-induced bleaching. In conjunction with the apoptotic gene downregulation, the immune response gene in acclimation samples showed pronounced upregulation, indicating high compatibility of deep corals to thermal changes. In recovery samples, the expression of the studied genes was similar to the expression of samples that underwent much less heat stress, which implies they were fully recovered. The expression of the cytochrome P450 gene showed no significant changes in all experiments. Overall, the findings suggest that P. harrisoni in the Persian Gulf is a thermal-tolerant species compared with counterpart species elsewhere in the world and can be classified as a thermally resilient coral. Thus, transplanting P. harrisoni in warm regions, where native corals have been subjected to climate change-driven mortality, might maintain the coral community under enhanced global warming scenarios.

Polypocephalus barsami sp. nov., a New Species of Polypocephalidae Meggitt, 1924 (Lecanicephalidea) from the Persian Gulf.

Although many batoid species, known as final hosts of lecanicephalidean cestodes, exist in the Persian Gulf, no knowledge regarding this cestode order is available for this region. This study is the first one focusing on this order in the Persian Gulf. A total of 11 cowtail stingrays, Pastinachus sephen (Forsskål), were collected from the north eastern Persian Gulf. Isolated cestodes were fixed in 10% seawater-buffered formalin and stored in 70% ethanol. For morphological examinations, worms were stained using acetic carmine; a subset was prepared for SEM. A new species of Polypocephalus Braun, 1878 was described. Polypocephalus barsami sp. nov. is the only species within its genus reported outside the waters of Japan, India, Sri Lanka, and Egypt in the Indian Ocean. Since the microtriches were not described in the generic diagnosis of Polypocephalus, the description of the microtriches is added based on the standardised terminology. Furthermore, the characteristics of this new specieswere discussedandcomparedwithin Polypocephalus, many species of which have poor descriptions. Polypocephalus barsami sp. nov. is the first report of the genus Polypocephalus in the Persian Gulf and the 15th valid species of its genus.

Bioaccumulation of heavy metals in eggshell and egg content of seabirds: Lesser (Thalasseus bengalensis) and Greater Crested Tern (Thalasseus bergii)

The Persian Gulf, the most important marine ecosystem, and its islands are negatively impacted by development and pollution. Different types of pollution, especially heavy metals in these habitats, may create risks to birds, influencing reproductive performance, survival, and behaviors.Heavy metals (Cd, Pb, Cr) were analyzed in two long-lived and top food web–level sea birds, Lesser (Thalasseus bengalensis) and Greater Crested Tern (Thalasseus bergii). The research was carried out during 2018 on Nakhiloo Island, located in Dayyer-Nakhiloo Marine National Park, northeastern Persian Gulf, Iran. The nests were selected randomly, and 40 eggs of colonially-nesting terns (20 eggs T. bengalensis and 20 eggs T. bergii; a single egg per nest) were collected. The concentration of heavy metals in eggshells and egg contents was studied to investigate whether bioaccumulation varies between the eggshells and egg contents and also varies in both species. There were significant differences in the amounts of Cd between eggshell and egg content in the Greater and Lesser Crested Tern. This difference was not significant in the concentrations of Pb between the eggshell and egg content in the Tern species. Concentration of Cr did not appear to accumulate in the egg content and was below detection limit. There were significant differences in the concentrations of Cd in the eggshells and egg content between the Greater and Lesser Crested Tern. The results serve to improve understanding and to evaluate the dynamics of heavy metals in eggshells and egg content in various avian species.

Orygmatobothrium persiense n. sp. (Cestoda: Phyllobothriidea) from the Arabian Smooth-Hound Shark Mustelus mosis (Triakidae) in the Persian Gulf.

A new species of Orygmatobothrium Diesing, 1863 was discovered from Mustelus mosis Hemprich et Ehrenberg in the north-eastern Persian Gulf. Orygmatobothrium persiense n. sp. is the fourth valid species of its genus and differs from its congeners by the number of the proglottids. In addition, the testes distributed in 3-4 rows deep in cross sections, the length of the cephalic peduncle, and a conspicuous bothridial cleft above the apical sucker distinguish the new species, respectively, from O. juani, O. musteli, and O. schmittii. This is the first time that a species of Orygmatobothrium is described and reported outside the Atlantic Ocean.

Neustonic zooplankton in the northeastern Persian Gulf

The Persian Gulf is an important area in terms of ecological values and fisheries resources. It also provides a supportive spawning and nursery areas for the finfish and shellfish communities, whose survival depends on the availability of the neustonic zooplankton. Neuston composition, abundance, and distribution were studied during two oceanographic cruises in autumn (Nov. to Dec.) 2012 and summer (Aug.) 2013 aboard R/V Ja Nay Band from 26 stations along the northeast Persian Gulf. Samples were collected in duplicate using a rectangular frame (300μm mesh net). Copepods (including copepodites) were the dominant constituents of the zooplankton and accounted for 56.7% and 69.2% of the total zooneuston populations during autumn and summer cruises, respectively. Among zooneuston, copepod biodiversity was relatively high with thirty-four copepod species in twenty two genera present. The other major groups of zooplankton in term of abundance were fish larvae and eggs 15.2%, urochordates 10.1%, decapods and other crustaceans 6.2%, cladocerans 3.8%, cnidarians 2.7% and chaetognaths 2.4% during the autumn cruise. In contrast, during the summer cruise, the other most abundant zooneuston were urochordates 7.5%, decapods 6.8%, cnidarians 6.1%, chaetognaths 3.8% and fish larva and eggs 1.5%. Zooneuston composition differed slightly in different cruises. Zooneuston abundance was slightly higher during autumn (mean of 295 ± 61 ind. m−3) than summer (231 ± 61 ind. m−3). Total zooneuston abundances were not significantly different (p > 0.05) in both spatial and temporal scales, but their copepod abundances were spatially significant (p < 0.05). Among marine insects, Halobates sp. was the new record for the Persian Gulf.

Variation in calcification rate of Acropora downingi relative to seasonal changes in environmental conditions in the northeastern Persian Gulf

There is a strong interest in understanding how coral calcification varies with changing environmental conditions, especially given the projected changes in temperature and aragonite saturation due to climate change. This study explores in situ variation in calcification rates of Acropora downingi in the northeastern Persian Gulf relative to seasonal changes in temperature, irradiance and aragonite saturation state (Ω arag). Calcification rates of A. downingi were highest in the spring and lowest in the winter, and intra-annual variation in calcification rate was significantly related to temperature (r 2 = 0.30) and irradiance (r 2 = 0.36), but not Ω arag (r 2 = 0.02). Seasonal differences in temperature are obviously confounded by differences in other environmental conditions and vice versa. Therefore, we used published relationships from experimental studies to establish which environmental parameter(s) (temperature, irradiance, and/or Ω arag) placed greatest constraints on calcification rate (relative to the maximum spring rate) in each season. Variation in calcification rates was largely attributable to seasonal changes in irradiance and temperature (possibly ~57.4 and 39.7% respectively). Therefore, we predict that ocean warming may lead to increased rates of calcification during winter, but decelerate calcification during spring, fall and especially summer, resulting in net deceleration of calcification for A. downingi in the Persian Gulf.

Morphological Variability of Liza klunzingeri (Day, 1888) from Bandar Abbas Port and Qeshm Island in Northeastern Persian Gulf

Morphological Variability of Liza klunzingeri (Day, 1888) from Bandar Abbas Port and Qeshm Island in Northeastern Persian Gulf

A study on plasma Testosterone levels in Abudefduf vaigiensis at the Northeastern Persian Gulf

A study on plasma Testosterone levels in Abudefduf vaigiensis at the Northeastern Persian Gulf

Length-weight relationships of five fish species from Hormozgan coastal waters (northeastern Persian Gulf)

Summary The study presents and describes the first length–weight relationships for five fish species: Lagocephalus inermis (Temminck and Schlegel, 1850); Chelonodon patoca (Hamilton, 1822); Ilisha megaloptera (Swainson, 1839); Pseudosynanceia melanostigma Day, 1875; and Chirocentrus nudus Swainson, 1839) from the coastal waters of Hormozgan in the northeastern Persian Gulf.

Acropora distribution patterns in the northern and northeastern Persian Gulf

Background Acropora species distribution patterns at Larak, Farur, and Khark Islands along the Iranian coast were investigated from October 2008 to November 2009 based on a previous study conducted on the taxonomy of Acropora by examining 1,169 colonies.ResultsThe analysis showed that the species diversity and evenness were low at the three islands, but the total percentage cover of Acropora was relatively high at Larak (38.52%) with lower cover at Khark (24.01%). The Acropora community at Larak Island was significantly dissimilar to those at Farur and Khark Islands, whereas the latter two possessed similar community structures. Chlorophyll a differences of Larak with Farur and Khark Islands coincided with Acropora community differences among these islands.ConclusionsRelatively high coral coverage found at the islands off the Iranian coast suggests important implications for coral reef resilience and mitigation (e.g., assisted migration) in response to changing environmental conditions, not only for the Persian Gulf but also for the world's coral reefs under the impacts of climate change.

Preliminary biological information of Scylla serrata (Forskål, 1775) (Brachyura, Portunidae) in the Persian Gulf and Gulf of Oman: a conservation priority

The status of the populations of the mud crab Scylla serrata (Forskal, 1775) is poorly known in the western Indian Ocean. Biological aspects of the species have been studied using 96 specimens collected between autumn 2009 and summer 2010 from the northwestern Gulf of Oman and 22 specimens collected in spring 2009 from the northeastern Persian Gulf. The population was found to be sparse in the northwestern Gulf of Oman (about 1 crab per hectare) and only one small population was recorded in the Persian Gulf. In total, 81.3% of the crabs in the Gulf of Oman were males, which may be a result of the breeding migration of females into offshore waters. The carapace width of the Gulf of Oman specimens ranged from 89.7 to 196.5 mm (males) and 91.7 to 170.1 mm (females). The smallest mature female measured was 12.4 cm in carapace width. The carapace width (CW)/weight (W) relationships in the crabs of the Gulf of Oman were calculated to be W = 2 × 1 0 − 5 CW 3 . 48 and W = 1 . 8 × 1 0 − 3 CW 2 . 52 for males and females, respectively. The gill chamber in many of the Gulf of Oman’s crabs was covered with the lepadomorph barnacles, Octolasmis cor (Aurivillius, 1892) and O. angulata (Aurivillius, 1894). Although, the reason of the low abundance of the crab in the Persian Gulf and the Gulf of Oman is still unknown, conservation programmes seem to be necessary.