Songkhla Lagoon Research Articles

Occurrence and abundance of microplastics in surface water of Songkhla Lagoon.

Microplastic (MP) pollution is now a global critical issue and has been the subject of considerable worry for multiple various types of habitats, notably in lagoons which are coastal areas connected to the ocean. MPs are of concern, particularly because floating MP in surface water can be ingested by a number of marine organisms. There are several lagoons along Southeast Asia's coastline, but Songkhla Lagoon is Thailand's only exit with a rich biodiversity. To date, there has been little research undertaken on MP in this lagoon, so there is a pressing need to learn more about the presence of MP in the lagoon's water. We investigate MPs in the surface water of Songkhla Lagoon, Thailand. Sampling took place at ten stations in the lagoon during the wet season in December 2022 and the dry season in February 2023. Samples were digested with hydrogen peroxide to remove organic matter followed by density separation using saturated sodium chloride. MPs were visually examined under a stereo microscope to describe and determine the shape, size, and color. Polymer type was identified using a micro Fourier transform infrared (FTIR) spectrometer. Moreover, the in-situ of water quality of the surface water was measured using a multi-parameter probe. A Mann-Whitney U test was performed to investigate the variations in MP levels and water quality parameters between the wet and dry seasons. Correlation analysis (Spearman rho) was used to determine the significance of correlations between MP and water quality (p < 0.05). MPs were detected at all ten of the sites sampled. The most abundant MPs were small size class (<500 µm, primarily consisting of fibers). Five types of polymers were seen in surface water, including polyethylene terephthalate, rayon, polypropylene, polyester, and poly (ethylene:propylene). Rayon and polyester were the dominant polymers. Additionally, the most dominant color of MPs in the wet and dry season was black and blue, respectively. The mean contents of MPs in the wet and dry season were 0.43 ± 0.18 and 0.34 ± 0.08 items/L, respectively. The Mann-Whitney U test suggested a significant difference between water quality in the wet and dry seasons (p < 0.05). Correlation analysis (Spearman rho) indicated a negative significant difference relationship between the MPs and the values of total dissolved solid (TDS) in the wet season (r = -0.821, p = <0.05), revealing that the large amounts of MPs may possibly be dispersed within surface water bodies with low TDS concentrations. Based on the overall findings, MP pollution in the surface water of the lagoon is not found to be influenced by the seasonal context. Rivers flowing into the lagoon, especially the U-Taphao River, may be a principal pathway contributing to increased MP pollution loading in the lagoon. The results can be used as baseline data to undertake further research work relevant to sources, fates, distribution, and impacts of MPs in other coastal lagoons.

Coastal Evolution of Satingpra Peninsula, Songkhla Province: Implications for Understanding Songkla Lagoon Formation

Songkhla Lagoon has been studied for decades, but there is no clear evidence of its origin. As a barrier to the lagoon, the Satingpra Peninsula plays a crucial role in understanding its formation. Eleven sediment samples from sand ridges and tidal flats on the Satingpra Peninsular were collected and analysed for granulometry and geochronology. Both coarse-grained and fine-grained quartz-rich fractions were utilised to prepare samples of aliquots. The optically stimulated luminescence (OSL) dating was performed using the single-aliquot regenerative dose method for a determined (deposited) age. In addition, previous research, geological surveys and geochronological data were combined to explain their formation in this region. The OSL ages in the present study indicated that the late Holocene regression occurred between 0.36 and 3.27 ka (ka stands for 1,000 years). Integrated with previous studies, recorded ages dating back to the mid-Holocene sea level rise (ca. 6.5 ka) and the subsequent late-Holocene decline, indicate that both the old lagoon and middle beach ridge exhibit a sand ridge formation that runs parallel to the shoreline, extending from the south to the north. The middle sand, in this study, formed from about 3.02 to 1.5 ka ago resulting in the lagoon being isolated from the sea during that time. The lagoonal tide led the deposition as the present tidal flat from 3.3 to 1.7 ka. About 2.19 ka ago, the inner and middle ridges formed due to wind-driven processes influenced by a dry climate. This was followed by a continued sea level regression, leading to the formation of the outer ridge around 1.5 ka ago when the sea level was 1.4 m below the present sea level. However, it’s essential to consider this sea level data in relation to the tectonic and human-induced land motions in the surrounding area. HIGHLIGHTS OSL ages, based on average dose model at the Northern Satingpra Peninsula were 1.04 - 3.27 ka. The old sand ridges of the Satingpra Peninsula prograde northward after mid Holocene sea level highstand. Paleo sea level based on wind-wave sediments contact was 1.4 m lower than present day at 1.46 ka. GRAPHICAL ABSTRACT

Microplastics and heavy metals in the sediment of Songkhla Lagoon: distribution and risk assessment

Heavy metal and microplastic (MP) contamination of aquatic systems is a major environmental issue that affects human health globally. Songkhla lagoon, the largest lagoon in Thailand, also faced with the environmental issues. Here, this study reported the occurrence of heavy metal and MP in 10 sites of sediment in the Songkla lagoon. From the microplastic separation, fibers were found at all stations at 68.24% (15.15 items/g) and fragments were found at 31.76% (7.05 items/g). The highest number of MP particles was found at the area near the mouth of the lagoon (5.4 items/g). The average concentrations (mg/kg) of heavy metal at all sites showed the following trend: Mg (732.54 ± 247.04) &amp;gt; Mn (176.74 ± 83.68) &amp;gt; Zn (29.36 ± 39.47) &amp;gt; Cu (12.31 ± 24.58) &amp;gt; Pb (11.07 ± 7.60) &amp;gt; As (5.64 ± 3.30) &amp;gt; Co (2.90 ± 1.38) &amp;gt; Cd (0.22 ± 0.17). Regarding the overall risk assessment of MPs in lagoon sediment in this study, the risk was categorized as high for the polymer hazard index. The ecological risk index found Cd and As to have high ecological risk. High EF values were observed for As and Cd, which indicated severe enrichment. Based on the Igeo calculation, the majority of sampling stations were unpolluted to moderately contaminated (Pb, Zn, Mg, and Co). Furthermore, there was no significant correlation between MPs and heavy metals, except for Zn (r = 0.697) and Cu (r = 0.61) (both p&amp;lt; 0.05). The results of this study might provide valuable data to develop conservation policies for coastal lagoon areas.

Microplastics in estuarine fish (Arius maculatus) from Songkhla Lagoon, Thailand

In this study, we investigate microplastic ingestion in different catfish (Arius maculatus) organs caught in Songkhla Lagoon, Thailand. Microplastics were extracted from gills, stomach, and tissue using alkaline solution (10% potassium hydroxide [KOH]). Physical characteristics including color and shape were examined under a stereomicroscope and polymer types were examined using Fourier Transform Infrared Spectroscopy (FTIR). The most common colors were blue and black, with sizes > 1 mm. Average accumulation in gills was 1.29 ± 0.17 particles/individual, stomach 1.77 ± 0.25 particles/individual, and tissue 1.97 ± 0.19 particles/individual. Surprisingly, accumulation was highest in tissue than other organs. Importantly, microfiber abundance was negatively correlated with stomach weight (r = –0.335, p < 0.05). Polymers were identified including polypropylene (PP), polyethylene terephthalate (PET), rayon, and copolymers (PP combined with PE). It is worth noting that textile fiber (rayon) also appeared in the stomachs of catfish due to the higher release of cloth fibers (microplastics) into sewers and the lagoon. Future research should focus on the socio-economic impacts and management strategies of plastic and microplastic.

A Confirmation Factor Analysis of the Potential Level Scale for Halal Tourist Sites in Lower Songkhla Lake

This research aims to examine the coherence between the potential levels of halal tourist attractions in the lower Songkhla lagoon area for Muslim tourists with empirical data. The sample consisted of 400 Muslim tourists. This research used questionnaire to collect the data which had a confidence value of Cronbach's Coefficient Alpha with a confidence value of 0.960. The researchers analyzed the structural validity of the potential levels about halal tourist attractions around the lower Songkhla lagoon for Muslim tourists by analyzing the second corroborative component using a statistical computer program. The second corroborative component analysis revealed that the potential levels of Halal Tourist Sites in the Lower Songkhla lagoon consisted of 6 components of equal importance with component weights of 0.78, 0.84, 0.83, 0.93, 0.90, and 0.87. The results of checking the consistency of the empirical component model found that the chi-square statistic is 391.24 at 259 degrees of freedom, the probability is 0.00, the relative chi-square statistic is 1.51, the Goodness of Fit Index (GFI) is 0.93 and the Adjusted Goodness of Fit Index (AGFI) is 0.90, the Comparative Fit Index (CFI) is 0.99, the Root Mean Square Residual (RMR) is 0.02 and the Root Mean Square Error of Approximation: RMSEA) is 0.04, which indicates that the potential levels of halal tourist attractions in the lower Songkhla lagoon area for Muslim tourists consistent with the empirical data and it consists of 6 components: Accessibility, Environment, Tourism Management, Facilities, Value, and Response.

Taxonomic note on Mesopodopsis tenuipes Hanamura, Koizumi, Sawamoto, Siow et Chee, 2008 (Crustacea: Mysida: Mysidae) from Songkhla Lagoon, with an update of its distribution in Southeast Asian Waters

Taxonomic note on Mesopodopsis tenuipes Hanamura, Koizumi, Sawamoto, Siow et Chee, 2008 (Crustacea: Mysida: Mysidae) from Songkhla Lagoon, with an update of its distribution in Southeast Asian Waters

Microplastic Accumulation in Catfish and Its Effects on Fish Eggs from Songkhla Lagoon, Thailand

Microplastics have been found to accumulate in freshwater, marine ecosystems, and biological organisms. The frequency of studies on microplastic contamination in organs has increased recently, although there have been relatively fewer investigations on fish eggs in Thailand. To extract microplastics from catfish samples for laboratory analysis (Osteogeneiosus militaris), we used 10% potassium hydroxide in the digestion process. A needle penetrated the fish eggs to investigate microplastic contamination. We examined microplastics under a stereomicroscope and used Fourier transform infrared spectroscopy to determine the type of polymer. We found microplastic contamination in organs, most commonly in the stomach (0.91 ± 0.13 items/g), followed by tissue (0.53 ± 0.09 items/g), and gills (0.30 ± 0.03 items/g) at the level of significance p &lt; 0.01. We found a total of 349 fish eggs with 27 items of microplastic. The dominant microplastic we found in the stomach, tissue, and gills of the fish, as well as in fish eggs, was of fiber shape. We noted that fragments were found only in the stomach and tissue of fish. The dominant color of microplastics was black in organs and blue in fish eggs. The common polymer types in organs and fish eggs were polyethylene terephthalate, polypropylene, and cellulosic fiber.

An annotated checklist of the species of Lopogastrida and Mysida (Crustacea: Peracarida) from Thailand and its adjacent waters

A compilation of mysid shrimps species found in brackish water to seawater has been carried out based on published records. The checklist includes the taxonomic position of each species, local distribution and depth range, the geographic zones and also the bibliographic references where they were recorded. Altogether 3 Lophogastrida and 52 Mysida species and 1 subspecies are listed. Most of them are distributed in the Andaman Sea (41 species), some in the Gulf of Thailand (13 species) and a few in the Songkhla Lagoon System (5 species). Mysids from the tribe Erythropini and Neomysini are the most predominant overall recorded species. Two of the recorded Mysida species are possibly endemic to the Songkhla Lagoon System (Deltamysis songkhlaensis and Nanomysis siamensis), whereas two species are endemic to the Phuket Island (Anisomysis phuketensis and Erythrops phuketensis). Previously, Rhopalophthalmus egregius was claimed to live in the Songkhla Lagoon System, however, further investigation show that this is not the case.

Bioengineering by the alien false mussel Mytilopsis sallei (Bivalvia: Dreissenidae) affects small-scale distribution pattern of benthic macroinvertebrates in an estuarine system

ABSTRACT The false mussel Mytilopsis sallei (Récluz, 1849) invaded the Songkhla Lagoon System in southern Thailand more than two decades ago. The false mussel forms dense beds, creating three-dimensional habitat structures on soft substrata which harbour a myriad of organisms. We compare a community of benthic macroinvertebrates in a habitat modified by M. sallei with a community in an unmodified habitat. The study focused on a canal feeding into the southern end of the lagoon system and covered three seasons (north-east monsoon season, dry season and south-west monsoon season) in a 12-month period. A total of 26 taxa were present in the modified habitat and 22 in the unmodified habitat. In the modified habitat, abundances of other byssally attached bivalves, flatworms and some species of amphipods were more than an order of magnitude greater than abundances in the unmodified habitat. Differences in the community composition between habitats were observed but were dependent on sampling location and time. Although the modified habitat hosted greater numbers of species and individuals in most comparisons, the Shannon–Wiener index and Pielou's evenness index were lower for this habitat as it tended to be dominated by a few taxa. The results highlight the role of M. sallei as a habitat engineer that promotes species richness and abundance of some benthic macroinvertebrates. Nonetheless, temporal variation in environmental drivers, especially salinity, might also be important in determining biodiversity in the studied estuarine system.

Photosynthetic Responses of Freshwater Macrophytes to the Daily Light Cycle in Songkhla Lagoon.

Macrophytes play an important role in the freshwater ecosystem. However, human activities and climate change are currently affecting aquatic lakes and species in various ways. The heterogeneity of macrophyte ecophysiology might lead to different responses to changing environments. To understand the photosynthetic responses of freshwater macrophytes to changes in light, six freshwater macrophyte species from Songkhla Lagoon were investigated. The results showed that there was a diurnal response of photosynthetic activities in all species. The Fv/Fm and ∆F/Fm' of all species decreased at midday (9 a.m.-3 p.m.) then recovered at 6 p.m. close to the 6 a.m. level. As well as alpha, the positive relation between alpha and light showed the adaptation of plants. The saturating irradiance (Ik) revealed that plants from different light regimes showed different responses to light and temperature changes. To maintain a positive carbon balance and cope with light and temperature conditions, macrophytes had strategies such as modifying light harvesting capacity and light use. This study provides a better understanding of the vulnerability of each species to environmental changes and photosynthetic responses that enable species from different light regime to adapt to changing light environments.

Redescription of Nanomysis siamensis W.M. Tattersall, 1921 (Crustacea: Mysida) after 100 years, with an update of its distribution in the Songkhla Lagoon System, southern Thailand.

Nanomysis siamensis W.M. Tattersall, 1921 is a shallow water mysid which was first described from the Thale Luang and the Thale Sap waters, Songkhla Lagoon System in southern Thailand. Recently, this species was captured further south, in the Thale Sap Songkhla waters. In this study, we provide updated records on spatial distribution of the species in the Songkhla Lagoon System. A total of 272 individuals of this species were observed, and illustrations of the body including all appendages are presented. Among them, the mandible, maxillule and maxilla are described for the first time. Morphological characteristics of N. siamensis are compared with other two known species of the genus Nanomysis.

The Occurrence of Microplastics in Sediment Cores from Two Mangrove Areas in Southern Thailand

Mangroves are areas that connect the land and sea, and are important to the ecosystem. They are important places for food sources and the habitat of aquatic fauna in the tidal areas. However, the existence of plastic debris poses a risk to the aquatic environment. This study aimed to investigate the accumulation of microplastics (MPs) in sediment cores from two mangrove areas. The first mangrove area is in the outer section of the Songkhla lagoon (SK), while the second is in the coastal area of Pattani province (PN). Sediment core sampling was performed from SK = 8 stations and PN = 5 stations. Surface enrichment of MP was observed, especially in sediments of 0–4 cm. MPs were found throughout the depth in both areas, while fewer MPs were found in deeper sediment core layers (p &lt; 0.05) at some stations inside the mangrove zone. Simple linear regression of the observed MPs and distance in the horizontal were found to be significant at SK within the mangrove zone with r2 = 0.79 (p &lt; 0.05). MP fibers were the most commonly found MP type in both areas and were less than 1 mm. Blue and black MPs were the most abundant colors found in both areas. The six polymer types reported in this study comprised polyethylene, rayon, rubber, styrene, Poly (vinyl acetate), and paint. The findings of the present study suggest that long-term monitoring of marine debris along coastlines is necessary to help improve national policies and measures related to marine plastic debris.

​Effect of Hydrilla verticillata in Feed on Production Performance and Carcass Characteristics of Thai Native Chickens

Background: Producing Thai native chickens through feed commercial is costly. To reduce the cost, native chicken could be fed with local plants or agricultural waste. Hyrrilla verticillate, a dominate macrophyte in Songkhla Lagoon, contain high crude protein and nitrogen free extract. Therefore, this research studied the use of Hydrilla verticillate in Thai native chicken diet on production performance, carcass characteristics and production cost. Methods: The experiment was executed in a completely randomized design (CRD) with 180 one-day-old commercial Thai native chicks. Four dietary treatments supplemented with 0%, 5%, 10% and 15% Hydrilla verticillata were formulated for three different phases of the experimental chickens: starter (1-4 weeks), grower (5-8 weeks) and finisher (9-12 weeks). Two chickens from each replicate were chosen for the carcass characteristics study. Result: During the starter phase, there was no notable effect shown among the chickens fed with the diet containing Hydrilla verticillata in terms of feed intake (FI) and body weight gain (BWG) (P greater than 0.05). The control chickens had best feed conversion ratio (FCR) (P less than 0.05), while the grower and the finisher periods, provided with different levels of Hydrilla verticillata, revealed no apparent differences (P greater than 0.05) concerning FI, BWG and FCR. Considering carcass characteristics, there were significant differences in live weight (LW) (P less than 0.05). But, no significant differences between treatments for hot carcass percentage, pectoralis majors, pectoralis minorstrip, thighs, wings, drumsticks and total edible carcass (P greater than 0.05). There were also statistical divergences regarding gizzard weight (GW) (P less than 0.05).

Population structure and reproductive biology of the mysid Nanomysis siamensis (Crustacea: Mysida) in Songkhla Lagoon system, southern Thailand

Songkhla Lagoon in southern Thailand is a large lagoon with brackish water where the mysid Nanomysis siamensis inhabit. N. siamensis has long been the dominant mysid species in this lagoon. However, nothing is known about the biology and ecology of N. siamensis. Here for the first time, we provide information about its demographic structure and reproductive biology in the Songkhla Lagoon system. We conducted monthly sampling from June 2017 to June 2018 at five stations in Thale Sap and seven stations in Thale Sap Songkhla. Individuals were classified into six categories. The monthly mean density ranged 8.44–807.33 inds./100 m2 in Thale Sap and 8.81–434.44 inds./100 m2 in Thale Sap Songkhla. The peak occurrence of this species was in May 2018 in Thale Sap. The population composition was as follows: juvenile 10.13%, immature males 13.45%, immature females 10.54%, mature males 26.19%, mature females 21.63% and ovigerous females 18.05%. The proportion of ovigerous females was statistically significant and brooding females in the nauplioid stage were more dominant than embryonic phase and post-nauplioid stages. Brood size varied from 1 to 17, the embryo diameter ranging from 0.2 to 0.4 mm and the lengths of the larvae ranged from 0.5 to 1.0 mm. There was a positive correlation between brood size and brood length with ovigerous female body length. Overall, mature males were predominant over the five population composition types, and reproduction in N. siamensis was observed every month.

Epitokous metamorphosis, reproductive swimming, and early development of the estuarine polychaete, Neanthes glandicincta Southern, 1921 (Annelida, Nereididae) on the east coast of the Malay Peninsula.

The reproductive and developmental characteristics of the nereidid polychaete, Neanthes glandicincta Southern, 1921, commonly recorded in tropical estuaries in the Indo-West Pacific, were examined from Malaysia (the mangrove area of Kuala Ibai, Terengganu) and Thailand (the Lower Songkhla Lagoon) on the east coast of the Malay Peninsula. Epitokous metamorphosis of fully mature males and females and their reproductive swimming behaviour were recorded based on ten Malaysian epitokous specimens, which were collected at night during spring tides in a period of January 2018 to March 2019. Six Thailand epitokes were obtained in February and March 2006 by the laboratory rearing of immature worms. Epitokous metamorphosis is characterised by the enlargement of eyes in both sexes, division of the body into three parts and modification of parapodia with additional lobes in the mid-body of males, and replacement of atokous chaetae in the mid-body by epitokous natatory chaetae, completely in males and incompletely in females. The diameter of coelomic unfertilised eggs in females was 100–140 µm. After fertilisation, each egg formed a jelly layer, inside which embryonic development progressed. Trochophores hatched out of the jelly layer, entering a short free-swimming larval phase followed by demersal life at the early stage of 3-chaetiger nectochaeta one day after fertilisation. Then, the larvae entered benthic life as juveniles, crawling on the bottom, at the late stage of 3-chaetiger nectochaeta two days after fertilisation. The results indicate that N. glandicincta has an annual life cycle, which is usually completed within an estuary with limited larval dispersal ability.

The Relationship between Salinity and Benthic Fauna Diversity and Abundance at Songkhla Port, Thailand

Jombodin, T.; Songkai, P.; Wichachucherd, B., and Rodcharoen, E., 2021. The relationship between salinity and benthic fauna diversity and abundance at Songkhla Port, Thailand. Journal of Coastal Research, 37(6), 1173–1180. Coconut Creek (Florida), ISSN 0749-0208. Benthic fauna plays an important role in marine ecosystems as the primary food for other aquatic animals, and this animal group helps reduce sediment nutrients by filter feeding. The aim of this study was to evaluate and explain the diversity and abundance of the benthic fauna community at the Songkhla port, where both human activities and environmental fluctuations affect this community. Benthic fauna and water samples were collected at 2-month intervals from January to November 2017. The results show that most physical parameters had wide ranges and varied by month. The benthic fauna in the Songkhla lagoon was observed in this study. The results showed a higher number of taxa compared with a previous study. Three phyla, namely, Annelida, Arthropoda, and Mollusca, had 25 taxa recorded in this study. Crustaceans were the most diverse (nine taxa) and abundant (2981 ± 313 ind/m2) group, followed by polychaetes (eight families, 2350 ± 288 ind/m2) and mollusks (eight taxa, 633 ± 200 ind/m2). Barnacles were the dominant group of crustaceans (2153 ± 758 ind/m2), whereas Serpulidae (1864 ± 647 ind/m2) and Mytilidae (447 ± 367 ind/m2) were the dominant families of polychaetes and mollusks, respectively. Cluster analysis showed that the distribution of benthic fauna and physicochemical water quality varied with similar patterns. Clustering gave two groups: for rainy season from November to January and for dry season from May to November. According to canonical correspondence analysis, salinity and transparency were the main environmental factors associated with the distribution pattern of benthic fauna in the area. In conclusion, the activities at the Songkhla port have not yet created problems for marine benthic fauna; instead, seasonal changes appear to drive changes in benthic fauna. However, future construction developments can affect the geographical area, complementing stresses from parameter changes at local scales.

Temporal and spatial patterns of abundance and occurrence of planktonic shrimps in the Songkhla Lagoon System, southern Thailand

Temporal and spatial distributions of planktonic shrimps from the hyperbenthos of Thale Sap and Thale Sap Songkhla lakes in the Songkhla Lagoon system, southern Thailand, were investigated using modified Riley push nets with a mesh size of 0.5 mm between June 2017 and June 2018. Three species of Mysida and two species of Dendrobranchiata shrimps were revealed, among which Nanomysis siamensis was dominant, representing more than 90% of the catch throughout the year. The Songkhla Lagoon system experiences extreme changes in temperature, salinity, pH, and water levels due to seasonal monsoons. A significant difference in the planktonic shrimp assemblages between Thale Sap and Thale Sap Songkhla was observed across the sampling months. Significant differences in the assemblage structure were also evident between Thale Sap and Thale Sap Songkhla and among sampling months. Dissimilar assemblage patterns were prominent temporally during the shift from southwest to northeast monsoon seasons and from the intermediate to southwest monsoon. Lake (Thale Sap or Thale Sap Songkhla) was the most important environmental parameter affecting occurrence patterns for N. siamensis, Mesopodopsis tenuipes, and Belzebub hanseni in the Songkhla Lagoon system. Salinity governed the spatial distribution of M. tenuipes and B. hanseni. Nanomysis siamensis was the only species that was regularly present in high abundance in Thale Sap and Thale Sap Songkhla over the entire salinity range. This suggest that N. siamensis is likely a resident species of the Songkhla Lagoon system.

Fishes of Thale Noi and its tributaries, South Thailand

Thale Noi is a small freshwater lake in the Songkhla Lagoon system in south Thailand. Songkhla Lake basin has been developed under the Thailand National Socio-Economic Plan with well-documented recent changes in its physical environment. The objective of this report is to update the current fish species that inhabit the Thale Noi. This report refers to native species only. Fish diversity was assessed along with the environmental alteration. The present study recorded 51 and 49 native species in 1982–1983, and 2005–2009 respectively, with a total of 54 species belonging to 26 families had been listed. The findings of this study could also be of great value as a starting point for further studies. Regular monitoring for species composition of Thale Noi is needed, and it is essential that the current data and all points of view be considered by decision makers.

Mysids resource from Songkhla Lagoon, southern Thailand

The first information about mysid in Songkhla lagoon system, southern Thailand, was reported in 1921 from Thale Sap water. In this present study, we try to give more information about the mysid diversity, species composition and abundance from Songkhla lagoon, southern Thailand. Sampling were conducted from June to November 2017 using a modified Riley’s hand-pushed net at 12 stations (5 in Thale Sap and 7 in Thale Sap Songkhla). Three species of mysids, Mesopodopsis orientalis Tattersal, 1908, Nanomysis siamensis W. Tattersall, 1921 and Rhopalophthalmus egregius Hansen, 1910 were recorded from Songkhla Lagoon. Nanomysis siamensis was the predominant species with total abundance 245.55 ind./m2, and the density was higher in Thale Sap than Thale Sap Songkhla. Monthly mean salinity showed a great fluctuation from 0.64 to 17 ppt, however no correlation between the abundance of N. siamensis with salinity.

A new species in the genus Heteromysoides (Crustacea, Mysida, Mysidae) from Songkhla Lagoon, southern Thailand

A new mysid,Heteromysoides songkhlaensis, is reported from shallow water in the Songkhla Lagoon, southern Thailand. The new species is closely similar toH. nanain having a triangular rostrum and the eyestalk without a process at the anteromesial corner. However, the new species can be readily distinguished fromH. nanaby three setae on the inner margin and five setae on distal margin of the second segment of the mandibular palp; the carpopropodus of the fifth and sixth thoracic endopod of the new species is composed of four articles, and the telson of the new species is distally rounded, shorter than the sixth abdominal somite, and 1.3 times longer than its basal width; the spines on the telson form elongated spines from the distal to posterior margin. The new species also resemblesH. dennisi,H. simplex, andH. stenoura; however, it differs by (1) the presence of a rounded distal margin of telson, and (2) absence of a sharp process on the distolateral corner of the eyestalk.