The Study of Dinophyta Species Diversity in the Coastal Waters of Lasbela, Baluchistan

Dinoflagellates are a monophyletic group of single-celled eukaryotes that are typically categorized as protists (Bjørneklett, 2018). They are present in both freshwater and marine environments (Telesh et al., 2021; Draredja et al., 2019; Carty, 2014; Not et al., 2012). They are distinguished from other groups by their distinctive traits, which include consistent flagellar insertion, coloration, and nucleus features (Lovko, 2008; Noga and Levy, 2006). The salinity, depth, and sea surface temperature all affect their numbers (Taylor et al., 2008). While a significant part of dinoflagellates are photosynthetic, but many of them also combine photosynthesis and prey ingestion (phagotrophy and myzocytosis) to become mixotrophic (Hansen, 2011). Dinoflagellates are among the largest groupings of marine eukaryotes in terms of species, although being much smaller than diatoms (Vincent and Bowler, 2020). In the phytoplankton community, dinoflagellates and diatoms are essential, particularly in shelf and near-shore seas (Hilaluddin et al., 2020). About half of the extant dinoflagellate species are heterotrophs that do not photosynthesize, and the other half are autotrophs with chloroplasts (Gómez, 2012; Sherr and Sherr, 2007). Dinoflagellate species are marine organisms’ endosymbionts that are crucial to the biology of coral reefs (Suggett et al., 2017). A few species of dinoflagellates, such Oodinium and Pfiesteria, are parasitic while the majority are unpigmented predators of other protozoa (Skarlato et al., 2018).

As part of their life cycles, certain dinoflagellates create resting stages known as dinoflagellate cysts or dinocysts; 84 of the 350 identified freshwater species and slightly over 10% of the known marine species exhibit this behavior (Bogus et al., 2014; Tang et al., 2021). Dinoflagellates are alveolates that have two flagella, which is a trait shared with bikonts (Boudouresque, 2015). Dinoflagellates are characterized by the presence of two flagella, which facilitate their forward motility and spin (Hu et al., 2015).

A total of 2000 living dinoflagellate species, including freshwater, marine, and parasitic species, are suggested by the present assessments (Le Bescot et al., 2016). The majority of dinoflagellates live in marine environments, with only 17% of all species having settled in continental waters. Planktonic species predominate in dinoflagellates, with benthic forms making up 8% of the total species (Gómez, 2012).

When specific dinoflagellates rapidly accumulate, the water will become visibly colored. This is called red tide, or a toxic algal bloom, and it can cause shellfish poisoning if people consume contaminated shellfish (Rodríguez et al., 2024; McGowan, 2023). Additionally, certain dinoflagellates show bioluminescence, mainly in the form of blue-green light emissions. As a result, some areas of the ocean glow blue-green at night (Santhanam, 2022). 

As to the classification of numerous scholars, the dinophyceae class is the largest class among all the Dinophyta classes. According to Lemonnier et al. (2016), the class Dinophyceae is made up of several family types, including Cerratiaceae, Dinophysaceae, Oxytoxaceae, Prorocentraceae, and Pyrocystaceae. Nine unique primary dinoflagellate orders can be distinguished using genetic and morphological data: Prorocentrales, Dinophysiales, Phytodiniales, Noctilucales, Suessiales, Peridiniales, Gymnodiniales, Suessiales, and Pyrocystales (Not et al., 2012).

The effect of natural components on phytoplankton dynamics has been the subject of numerous studies (Boney, 1989; De Huszar and Nina, 1998; Kagalou et al., 2008; Hassan et al., 2008).

This study was conducted to evaluate the phytoplankton diversity assemblages in the coastal waters of Lasbela, Baluchistan. Investigations were also conducted into annual variations in the taxonomic composition of phytoplankton, the proportion of phytoplankton in the sample, and a comparison of the physicochemical characteristics of phytoplankton at various sampling locations.

The sampling location the Miani Hor lagoon was selected in order to examine the phytoplankton species for seasonal variations (inshore water 25°45.151′N, 66°55.966′E, and offshore water 25°45.539′N, 66°53.888′E) (Fig. 1).

Data on phytoplankton were collected monthly over a period of six months in order to examine seasonal fluctuations. The monsoon season runs from May to August 2020; the post-monsoon season runs from September to December 2019; and the pre-monsoon season runs from January to April 2020.

At both locations, samples were collected using a boat towing a phytoplankton net with a mesh size of 55μm horizontally across a 100 m depth beneath 0.5 meters of water. The boat was being pulled at a steady four knots per hour. The filtrate of the plankton net was immediately moved to a L-1 bottle and preserved with 5% formalin.

The salinity, temperature, and pH of the seawater from both Miani Hor sample stations were also collected in order to evaluate the seasonal physical and chemical characteristics. A thermometer, a refractometer, and a portable pH meter were used to measure the water’s temperature, salinity, and pH in-situ. Phytoplankton species were observed using a microscope (Wetzlar XLZPN).

A variety of literature, including Hoque et al. (1999), Chaghtai and Saifullah (1988, 2001), Richard (1987), Fritsch (1961), Prescott (1962), Kasymov (2000), and Tiffany and Britton (1971), were used to identify phytoplankton samples.

In order to analyze total phytoplankton abundance, cells L-1 were used which was then expressed as a percentage of total phytoplankton abundance. Since there were many species within each genus, the number of species within each genus was counted instead of the number of species within each particular species.

The study presents the phytoplankton composition of Miani Hor, the offshore and inshore waters of Balochistan, collectively with information on its more abundant seasonal flora. During the study period, which range from September 2019 to August 2020, the various species dinoflagellates were observed in samples taken from both the open sea and the lagoon. From the two sampling locations, the dinoflagellate species were identified.

Throughout the post-monsoon season, higher quantities of the phytoplankton algae group Dinophyta were found in inshore waters (59.25%) and lower concentrations (40.75%) in offshore waters (Fig. 2A). During monsoon season, a greater percentage of the phytoplankton species were found in inshore waters (62.70%) than in offshore areas (37.30%) (Fig. 2B). Whereas during the pre-monsoon season, 48.03% and 51.97% of the Dinophyta group’s members were found in inshore and offshore waters, respectively (Fig. 2C).

The number of phytoplankton species found in the inshore and offshore waters of Miani Hor, Balochistan, was found to be 2782 x 102 cells l-1. This data was collected between September 2019 and August 2020. The density of Dinophyta (dinoflagellates) in the same waters was found to be 1131 x 10 2 cells l-1.

In Miani Hor Balochistan’s inshore and offshore waters, a total of three seasons-post, pre, and monsoon the presence of phytoplankton species that are members of the Dinophyta group (Fig. 3). The variety of phytoplankton species found in large quantities in three seasons of inshore (52.38%) and offshore waters (47.62%) near Miani Hor, Balochistan.

Seasonal variation in phytoplankton density due to roughness of sea, collection was not possible in June and July, so the data does not accurately depict phytoplankton density. The seasons were classified as post monsoon (September 2019 to December 2019), pre monsoon (January 2020 to April 2020), and monsoon (May 2020 to August 2020).

The Dinophyta in this study has a broad spectrum of taxa with different structural variants. Between September 2019 and August 2020, a large number of species were seen in very high densities in both inshore and offshore waters. A number of species have been identified as members of the group Dinophya, including Ceratium arcticum, C. azoricum, C. furca, Dinophysis acuta, Dinophysis sp., and Prorocentrum micans.

Post-monsoon season at Miani Hor saw the highest growth of phytoplankton species, while pre-monsoon and monsoon seasons showed the lowest ratio. The highest ratio of Ceratium furca was seen in all three seasons.

A statistical analysis was performed, after counting each of the sample. Using the Simpson diversity index equation, the diversity index (D) was determined:

D = Σ (n − 1)/(N – 1)

where n is number of certain species of organism and N is the total number of members of all species within a family. An organism or family has very low diversity, according to the diversity index, if it is found in the range between zero and one, and very significant diversity, if it is found in the range between one and two.

During the post-monsoon season, 5 Dinophyta families were identified in both inshore and offshore waters (Fig. 4A) The Protoperidiniaceae and Prorocentraceae families have the highest diversity values in offshore water among all the Dinophyta families, with D= 0.998 in the figure. Ceratiaceae, the second most divergent family, showing D= 0.820 diversity values in inshore water and D= 0.794 in offshore water. Throughout the season, the family Ostreopsidaceae showed the least diversification of all the families, with D= 0.536 in inshore water and D= 0.389 in offshore water (Fig. 4B).

During the monsoon season, 11 Dinophyta families were identified in both inshore and offshore waters. In inshore waters, the families Protoperidiniaceae and Pyrocystaceae have the highest diversity among all over the families in the Group Dinophyta, with D=1.000 in the Figure 4C. Ceratiaceae, the second most divergent family, showing D= 0.657 diversification in inshore water and D=0.728 in offshore water. Throughout the season, the families Gymnodiniaceae and Oxytoxaceae showed very little diversification, with D= 0.000 in inshore water and= D 0.000 in offshore water across all families (Fig. 4D).

During the premonsoon season, 13 Dinophyta families were recorded in both inshore and offshore waters (Fig. 4E-F). In inshore water, the family Ostreopsidaceae, Protoperidiniaceae and Pyrocystaceae have the highest diversity among all the Dinophyta families, with D=1.000 and D = 0.333 in the figure. In offshore water the family Metacylidiaceae and Oxytoxaceae shown the highest diversity value with D= 1.00. Throughout the season, the family Kofoidiniaceae showed least diversity among all the families, with D=0.037 in inshore water and D= 0.031 in offshore water (Fig. 4F).

The current study extends data on the abundance and distribution of important dianoflagellate taxa in relation to environmental factors. Seasons appear to affect the number of phytoplankton, with a uni-modal distribution peak taking place in the northeast monsoon between October 2019 and February 2020 (Béjard et al., 2024; Vidal et al., 2024). This might be due to the significant upwelling that often takes place in the Arabian Sea’s central and northern regions, which controls the distribution and abundance of phytoplankton in the region and boosts primary output (Chowdhury et al., 2021; Moffett and Landry, 2020; Thara Sajeev, 2011).

Although upwelling along the Pakistani coast is unknown, wind-induced convective mixing and upsloping of nutrient-rich water are the causes of the high productivity in the northern Arabian Sea during the northeast monsoon period (Cicily and Nandan, 2015; Banse, 1968; Schapira et al., 2008; Uitz et al., 2010). Rivers contribution of dissolved nutrients has an impact on the coastal waters high primary productivity (Barber et al., 2001; Cebrián and Valiela, 1999). The Porali and Windor seasonal run-off rivers discharge into the study area along the coastal belt (Saifullah and Rasool, 2002).

Numerous species of dinoflagellates were collected at the Miani Hor in the lagoon and the adjacent open sea (Rasheed et al., 2019; Latif et al., 2013). The most prevalent species during the pre-monsoon season (46%) were phytoplankton species. In the post-monsoon and monsoon seasons, it was 31% and 23%, respectively. Studying diatoms in Felent Creek, Turkey, Solak et al. (2012) found that species richness was higher in the winter than in the summer.

At Miani Hor, the pre-monsoon season had the highest growth of phytoplankton species, while the monsoon season saw the lowest ratio. Over all three seasons, Prorocentrum micans demonstrated the greatest ratio. Ceratium furca was the most abundant ratio across all three seasons, coming in subsequent.

Numerous species (Prorocentrum micans, Dinophysis sp., Ceratium azoricum and Dinophysis acuta) exhibit extremely high ratios in both inshore and offshore waters during the transitional period of September 2019 to August 2020.

The Arabian Sea appears to be significantly impacted by sea level rise and global warming, which alters seasonality, intensifies the monsoon seasons, and increases productivity (Le Mézo et al., 2017; Goes et al., 2005).

Numerous physical factors, such as precipitation, inland runoff (volume of fresh water), climatic seasonality, sea surface temperature, acidification, etc., have an impact

on the parameters that determine the vertical water column since sea level is generally rising due to global warming (Riebesell, 2004; Moore et al., 2008).

Since there is currently little information available regarding the phytoplankton composition and abundance in the Maini Hor Lagoon, the existing data would serve as a foundation for future research in the area.

The Vice Chancellor of Lasbela University of Agriculture, Water, and Marine Science is acknowledged by the authors for his steadfast assistance in providing the facility. We also acknowledge the support provided by the LUAWMS, Faculty of Marine Science staff in the preparation of this manuscript.

The study received no external funding.

The authors have declared no conflict of interest.