QUINQUENNIAL ANALYSIS OF HARMFUL ALGAL BLOOMS IN THE ARABIAN SEA OFF THE INDIAN COAST FROM THE PAST DECADE

Abstract

The complexity in the ecological system is being catalysed by climate change and anthropogenic activities.?? The occurrence of Harmful Algal Blooms (HABs) along the India’s coastline becomes a point of concern when we are looking forward to tapping the natural resources for achieving the target of food security.? In this article we analyse the occurrence of major HABs along the India’s coastline and identify key areas that have reported the major occurrence.? The research was analysed by using satellite data and various parameters such as temperature, salinity in the waters adjacent to the India’s western coastline majorly.?? The study settled the trade-off between the opportunity cost of analysing such incidence with the relevance in terms of causing harm to the economic and food security interest of the nation. ?The water was found to be suitable for the occurrence of HABs in terms of environmental factors, however the nutrients were found to be a limiting factor. ?The study concludes that the occurrence of HABs in the waters along the western coastline are not significant and can be subsumed in other available Early Warning Systems (EWSs).

Introduction

As compliance certification and quality checks takes a central stage in managing food security and protecting human health the issue of Harmful Algal Blooms (HABs) comes as a topic of interest across the globe. ?A recently concluded workshop earlier this year organised by the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) of the United Kingdom and the ICAR- Indian Council of Agricultural Research Central Marine Fisheries Research Institute (CMFRI), India led to the discussion and use of the ‘One Health Framework’ to integrate key issues in animal, environmental and human health. ?This led to a series of discussion on the threats the sea food- consumers would be facing. ?Subsequently the book “Joint Technical Guidance for The Implementation of Early Warning Systems for Harmful Algal Blooms”, edited by Esther Pareja Garrido , 联合国粮农组织 of the United Nations and Karen Englander, Ph.D. , 加拿大多伦多大学 was analysed to understand the implication of HABs across the globe and its implication along the Indian coastline and its associated waters.

As global warming and climate change accelerates, and anthropogenic activities increases, the chances of “Harmful Algal Blooms (HABs)” becomes significant. ?HABs includes proliferation of microalgae in water that causes effects that are perceived detrimental by humans.[1] ?These detrimental effects are but not limited to water discolouration, massive fish kills, contamination of seafood with toxins, altering of ecosystem services. ?When it comes to industrial aspects these effects are centred around economy and human health. ?The affected zones are desalination system, the seafood industry, fisheries and aquaculture activities, tourism, and maritime facilities such as ports.[2]

The reason why the HABs causes such impact is due to their ability to cause environmental stress by reducing dissolved oxygen in seawater causing hypoxia or anoxia and by expanding dead zones.

?When this proliferation of microalgae occurs it majorly causes shellfish poisoning syndrome in filter feeders who have a bio-accumulative property.? It thus becomes significant to adhere to policies on seasonal and decadal forecast with respect to changing marine environment to sustain and support the coastal industries and food security. ?There are various projects being conducted around the globe that the book discusses about, for example European Union Interreg Atlantic Area funded PRIMROSE project[3], Intergovernmental Oceanographic Commission (IOC) HAB Programme’s Intergovernmental Panel on Harmful Algal Blooms (IPHAB, or the “Panel”) to name a few. ??

?The impact of HABs on the marine environment and the associated community is so immense that it has been specially focussed as Early Warning System (EWSs) in Sendai Framework for Disaster Risk Reduction 2015-2030 [4], and Paris Agreement (Article 7, paragraph 7c)[5].

The HABs occurrence are impacted by emerging anthropogenic pressures including climate change, ocean acidification, nutrient input, coastal development and the vectors for species transport.[6]? ?While some ancient tribal communities observing signs in the oceans have been acknowledged in the book, we would analyse the available satellite data in this article. ??The endpoint of concern is the occurrence of HABs in the Indian ocean region which should be calculated based on the trade-off between the cost i.e., the expense of observing/monitoring, the efficiency and the requirement of the detection in the region of concern.

To understand and develop our methodology for achieving the desired end state and to settle the trade-off between the opportunity cost and the relevance we would analyse the two case studies given in the book. ?The book has highlighted about the Mediterranean Sea (MS) with its semi-enclosed and oligotrophic nature. ??The growth of phytoplankton is limited in the concerned geographical area due to the nutrient availability and inorganic phosphorous concentrations which restrict primary production. ?The concurrence of the zone has complex interaction due to inputs from populated MS coastal area which determine variables such as nutrient availability.? ?In the region there has been reporting of blooms in the nearshore environment, such as in harbours, marinas, pocket beaches and confined areas such as bays. ?The factors which contribute to such events include presence of low turbulence, high water residence times (for example, up to 20 days due to the mild effects of tides in the area) and low advection in comparison with open waters. Apart from these the coastal areas are fed by river and groundwater discharges, deposition from the atmosphere, and upwelling of deep nutrients.?

But the major factor that is supporting the higher frequency of the HABs in the region is the high nutrient availability in these enclosed areas, which is five to ten times greater than the nutrient concentrations typical of open water areas. ?

The above-mentioned factors maintain phytoplankton biomass and support the growth of toxic species under favourable conditions for a prolonged period.

The second case study that the book discuss about is the HAB occurrence in Oman in 2018. ?The event did not cause large scale fish mortality but disrupted the operations of some desalination plants located along the coast such as Al Ghubra desalination plant and Majis desalination plant. ??The Sea of Oman is marginal and influenced by monsoonal-driven circulation and biogeochemical processes in the adjoining Arabian Sea.? It has dynamic circulation process with coastal upwelling, seasonal formation of mesoscale eddies.? As per the book the nutrient input from river discharge or run-off from land do not play a significant role in HABs formation. ?However, according to the authors, the HABs are due to cross shelf transport processes.

From the above two case studies discussed in the book it can be concluded that the HABs are dependent on temperature, upwelling regions, riverine inputs that brings anthropogenic nutrient loading, including agricultural runoff and sewage. This has been illustrated in the figure 1.

The book enlightens about certain countries who have developed a robust mechanism to tackle the occurrence of HABs in their waters and a summary of it has been given in Table 1, while some countries have dedicated projects, to name a few MediOs in France, Ebitox and OstreoRisk in Spain and the Interreg Med coordinated project M3-HABs.[7]

Taking the learnings from the book we shall be analysing the available satellite data to understand the physicochemical variables in the western coast of India and see for favourable environment in the water column spatially to understand the future occurrence of HABs in the coastal waters along the India’s coastline. The western coast of India has reported the maximum occurrence of HABs in the past and thus has been analysed in the present study (figure 2).

Methodology

We analysed the reported occurrence of the HABs across the globe and first analysed the reported occurrence of the blooms from 1800-2023 by UNESCO Ocean UNESCO UNESCO-UNEVOC IOC-UNESCO Harmful Algae Information System (HAIS). ?This is presented in figure 3.?

Then we analysed the reported occurrence of HABs in the coastal waters of India from the past 2 decades (2023-2000). ?A total of 24 events have been recorded so far in past 23 years. ?While only one event that occurred in 2014 that was only reported but with no identified location. Most of the events occurred in offshore areas of the Arabian Sea. ??This has been illustrated in figure 2.

We then used the available satellite data to analyse the major variables discussed in the book and see if there is any correlation of ambient environmental variables that might support the occurrence of large scale HABs in the coastal waters of the Arabian Sea.

We have used the Ocean Data View (ODV) software for the analysis of the satellite data. ?We analysed the quinquennial seasonal variability of the Chlorophyll a concentration along the western coastline of India based on the monsoon data. ?The data has been selected that is specific to Indian subcontinent monsoon.

For regional studies the variables emphasised were temperature and salinity which are correlated with each other in impacting the coastal biodiversity.? ?We have collected and compiled available observational satellite data for this case. ?Based on the reported hot spots where HABs can occur or have occurred in the past decade, has been studied for the present article. ?HABs occur in certain regions, and we have selected the regions of Arabian sea where the past trend has been observed the most. ?We selected the Kerala Coast for our present study for the analysis of temperature and salinity with changing depth and when going away from the coast towards the open sea since the major reported occurrence of HABs from the past years have been majorly reported off the Kerala coast (figure 2).? ?We also analysed the isosurface distribution of temperature all along the western coast of India for the year January 2021-January 2022 in the present article.

Results

As seen in the figure 3, major occurrence of such blooms have been reported across the North Atlantic Ocean, North and South Pacific Ocean, Canary basin, Mediterranean Sea and the South China Sea.

The salinity in the western coast of the Indian coast has been ranging in 24-40 PSU (Practical Salinity Unit) while the temperature has been ranging between 23-30° C (figure 4).

The higher chlorophyll a has been recorded mainly in the June to November of the year (figure 5.1-5.3). ?This coincides with the South-west monsoon that brings nutrients from the land to the coast.

Off the Kerala coast the water is in the range of 15-35 °C in the depth range of 0-100 m, while salinity range between 20-40 PSU in the depth range of 0-100m. ?While along the coast a section distance of 1200 km was selected and upto a depth of 200 m where the change in water temperature has been analysed the temperature ranges between 29-15 °C (figure 6).

The overall temperature and salinity profile of the western coast of the Indian ocean upto a depth of 4000 m indicates that the salinity ranges from 31.5 PSU to 38 PSU in the upper 100 m depths and then gradually narrow downs to a very small range upto the depth of 1000 m. ?Similarly, the temperature profile is in the range of 35-20° C in the upper 150 m depth and gradually narrows down to near freezing temperature in the depth range of 750-2000 m (figure 7).

The overall Chlorophyll a concentration, Net Primary Productivity (NPP) and the Dissolved Oxygen (DO) concentration in the western coast of India was also analysed from the year 1950-2022. ?The chlorophyll a concentration has remained at the higher side along and off the Gujrat coast, in the range of 1.5-2.5 mg/m3 which is followed by high net primary productivity (mg/m3) and dissolved oxygen mmol/m3 (figure 8).

Discussion

Based on the observation of the available satellite data it can be understood that the temperature and salinity of the waters either near the coast or off the coast of India are ambient for the occurrence of the HABs.

As there is high chlorophyll a occurrence in the coastal waters during the months of June to November, it can be understood that the monsoon pattern in the Indian subcontinent brings nutrient rich water from the land in addition to agricultural runoff and sewage from the land which provides an opportunity for growth of such phytoplankton species that are present in the waters of the Arabian Sea. ?Moreover, the waters are oligotrophic in nature meaning they are dependent on the nutrient input from land for the proliferation of phytoplankton to occur.

The technical guidance of the book offers us with factors that support the occurrence of blooms in the waters. ?For example, the technical guidance of the book informs that the ambient temperature of HABs is from 20-30° C. ?While the salinity has been ranged from 20-40 PSU for a broad region of species. ?The water needs to be calm and shallow for the occurrence of HABs. ?Such geographical support has been seen in areas which have almost closed geographical boundaries where there is high nutrient input, ambient physicochemical variables and the presence of phytoplankton species that can cause HABs. ?While such physicochemical variables are present here the nutrient input act as a limiting factor in the concerned geography.

As India’s Blue economy framework looks to tap the aquaculture and mariculture potential along the Indian coastline the HABs can have economic impacts if the sale of high-risk fish species cultured have been banned by the import countries. ?Apart from causing mass scale mortality in the natural and the cultured fishes where it occurs the HABs can have a significant impact on the filter feeders who have bioaccumulation property. ?This can have long term impact on the industrial as well as societal impact as the cultured food which represent a valuable source of protein and revenue for many coastal communities.[8]

As learnt from the book the occurrence of coastal blooms is dependent on seasonal phenology that is dependent on the physical and environmental forcing. ?The occurrence of bloom is dependent on upwelling regions, the waters are dependent on the nutrient availability that comes after a prolonged period of draught through the riverine input. ?As we can see from figure 3 the occurrence of HABs mainly occur around the waters of Europe[9], North America, Pacific Mexican coast [10]. ?These sites can be correlated with the established upwelling sites or sites having nutrient input from the land.

It must be noted at this point that while in the nutrient rich waters the HABs can occur[11] , they can also occur in nutrient-poor waters [12]. ? This process become complex with climate change and changing coastal environment.

Following the past trend and the available satellite data it can be understood that the occurrence of HABs in the coastal waters of the western coast of India that can cause economic loss is not a major point of concern at present.

However, as the ecological complexities comes into picture and its catalyst effect caused by climate change, we need to reform a policy framework that could be arranged as a subset of early warning system in the sites of concern.?

As we move towards tapping the resources in the coastal environment both spatially and temporally it becomes imperative to understand the importance of evolving early warning system to improve our resilience against such ecological phenomenon. ?The satellite data to be recorded depends on the cloud intensity of the region and thus are mostly supported by ground truthing through reporting of mass fish kill occurrence through the public media or observations in change in water colouration by coastal communities and other stakeholders.

In the present study we also correlated our study with the reporting of the occurrence in the daily newspaper. ?An example to consider here is the reported mass fish killing of about three tonnes of fish at the backwaters in the lagoons adjacent to the Kothandaramar temple in Dhanushkodi, Tamil Nadu and was quite similar to the incident that occurred on the seashore in the Gulf of Mannar in August to October. ?The probable point for such mass kill was suffocation due to oxygen depletion and high temperature was pointed by the Scientist in-charge of the event.? While the Jelly fish have been reported along the Coromandel coast during January- March in 2019 with a parallel event occurring on the New Jersey coast (US) as well. The washed-up species of Jelly fish are drifters and depend on the winds and currents for their movement.? ?The other locations along the Indian coastline that has been reported are Goa that had sighting of such venomous jelly fish organism in November-December 2017,? August, 2018. ?While Mumbai had reports in August 2018. ?This concludes understanding the ecological environment more significant for forecasting the occurrence of such natural events.

The Department of Aquatic Biology and Fisheries, University of Kerala in the year 2012 carried out a biodiversity survey along the southwest coast of India during the post-monsoon season?period where the fishing trawlers were facing difficult time due to nets getting clogged with jellyfish. ?

The masses of jellyfish have forced the shutdown of nuclear plants in several countries by choking the water intake filters. ?

There are 23 locations along the Indian coastline which have witnessed the jellyfish aggregations and beach strandings in the past four decades.[13]? ?These strandings can be correlated to any important physical infrastructure, or industrial settings for any possible damage in the future.

Conclusion

The Early Warning System should be initiated only when there is reported occurrence of mass fish kills or reported colour change in the water during the season. ?The satellite data should be used in key areas which are vulnerable to the effect of HABs causing economic and food security loss. ?So to summarise as per the available data it can be substantially concluded that the occurrence of HABs though prominent in the waters of Mediterranean sea, North Atlantic Ocean or the South China Sea, the waters in Arabian Sea of India’s interest haven’t got much reported HABs occurrence in the past. ?The situation can change with changing climate and the policy recommendation is that the occurrence of HABs shall be subsumed in early warning system that are currently available and in use.

[1]? Intergovernmental Oceanographic Commission, IOC HAB Programme, In: The Intergovernmental

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[3] Interreg Atlantic Area, “Predicting the Impact of Regional Scale Events on the Aquaculture Sector (PRIMROSE)”, In: European Regional Development Fund, Potsdam, Germany, 2023. www.shellfishsafety.

[4] United Nations, Office for Outer Space Affairs UN SPIDER Knowledge Portal. In: Risks and Disasters, Early Warning Systems. Vienna, Austria, 2023. www.un-spider.org/risks-and-disasters/early-warning-systems#no-back .

[5]? United Nations, United Nations Climate Change, In: United Nations Framework Convention on Climate Change, Bonn, Germany,? 2023. https://unfccc.int/sites/default/files/english_paris_agreement.pdf .

[6] McKenzie, Cynthia H, Stephen S Bates, Jennifer L Martin, Nicola Haigh, Kimberly L Howland, Nancy I Lewis, Andrea Locke, et al. “Three Decades of Canadian Marine Harmful Algal Events: Phytoplankton and Phycotoxins of Concern to Human and Ecosystem Health.”, Global Harmful Algal Bloom Status Reporting 102 (February 1, 2021): 101852. https://doi.org/10.1016/j.hal.2020.101852 .

[7] Drouet, K, C Jauzein, S Gasparini, A-S Pavaux, E Berdalet, S Marro, V Davenet-Sbirrazuoli, R Siano, and R Lemée, “The Benthic Toxic Dinoflagellate Ostreopsis Cf. Ovata in the NW Mediterranean Sea: Relationship between Sea Surface Temperature and Bloom Phenology.” Harmful Algae 112 (February 2022): 102184. https://doi.org/10.1016/j.hal.2022.102184 .

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[8] Darius, Hélène Taiana, Mélanie Roué, Manoella Sibat, Jér?me Viallon, Clémence Mahana Iti Gatti, Mark W Vandersea, Patricia A Tester, et al. “Tectus Niloticus (Tegulidae, Gastropod) as a Novel Vector of Ciguatera Poisoning: Detection of Pacific Ciguatoxins in Toxic Samples from Nuku Hiva Island (French? Polynesia).” Toxins 10, no. 1 (December 21, 2017). https://doi.org/10.3390/toxins10010002 .

[9]Hasle, G R, C B Lange, and E E Syvertsen, “A Review ofPseudo-Nitzschia, with Special Reference to the Skagerrak, North Atlantic, and Adjacent Waters.”, Helgol?nder Meeresuntersuchungen, 50, no. 2 (June 1, 1996): 131–75. https://doi.org/10.1007/BF02367149 .

[10] Ernesto Garc?′a-Mendoza, David Rivas, Aramis Olivos-Ortiz, Antonio Almaza′n-Becerril, Carolina Castan?eda-Vega, Jose′ Luis Pen?a-Manjarrez, “A toxic Pseudo-nitzschia bloom in Todos Santos Bay, northwestern Baja California, Mexico”, Harmful Algae 8 (2009): 493–503.

[11] Spatharis, Sofie, Daniel Danielidis, and George Tsirtsis, “Recurrent Pseudo-Nitzschia Calliantha (Bacillariophyceae) and Alexandrium Insuetum (Dinophyceae) Winter Blooms Induced by Agricultural Runoff.” Harmful Algae 6 (November 1, 2007): 811–22. https://doi.org/10.1016/j.hal.2007.04.006 .

[12] Collos, Yves, Béatrice Bec, Cécile Jauzein, Eric Abadie, Thierry Laugier, Jacques Lautier, Annie Pastoureaud, Philippe Souchu, and André Vaquer, “Oligotrophication and Emergence of Picocyanobacteria and a Toxic Dinoflagellate in Thau Lagoon, Southern France.” Journal of Sea Research 61 (January 1, 2009): 68–75. https://doi.org/10.1016/j.seares.2008.05.008 .

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[13]Siddique, Alfisa, Jasmine Purushothaman, Rakhesh Madhusoodhanan, and Chelladurai Raghunathan, “The Rising Swarms of Jellyfish in Indian Waters: The Environmental Drivers, Ecological, and Socio-Economic Impacts.” Journal of Water and Climate Change 13, no. 10 (October 20, 2022): 3747–59. https://doi.org/10.2166/wcc.2022.245 .

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