Hydrographical Observations during a Red Tide with Fish Mortalities at Masirah Island, Oman

Abstract

Harmful Algal Blooms (HABs) can have a significant impact on the distribution and survival of coastal fishes and invertebrates, and consequently they can affect local economies where fishing is an important activity. In October 2005, extensive algal blooms with brownish/orange discoloured water and fish mortalities were observed east of Masirah Island. Satellite images revealed cooler upwelled surface water along a broad front just prior to the event, followed by a gradual warming period coinciding with the mortalities. Depth profiles of dissolved oxygen (DO), temperature, salinity and pH taken on 19th October (during the fish mortality event) showed a pronounced thermocline at ~15 m depth and minimum DO of 0.82 ml/L at 25 m depth, and a slight improvement in DO to 1.3 ml/L was measured on 22nd October (after the event). Demersal fishes of several families were prominent among mortalities. No bacterial infestation was found in fish samples and no human poisoning was reported. Planktological data showed that marine dinoflagellates Noctiluca scintillans and Prorocentrum micans and toxic blooms of cyanobacterium Trichodesmium erythraeum were present.

Aquaculture in coastal urbanized areas: A comparative review of the challenges posed by Harmful Algal Blooms

“…The SW monsoons are known to cause dinoflagellate and cyanobacteria specific HABs in the Arabian Sea due to strong winds which cause the water to mix leading to high nutrient enrichments, strong upwelling along the coastal margins in the south of Oman, higher sea temperatures and river discharges (i.e. October 2005 in Table 2) (Al Shehhi et al, 2014;Al-Azri et al, 2012;Burt et al, 2016;Busaidi et al, 2008).…”

Fish Kill Incidents and Harmful Algal Blooms in Omani Waters

“…Hydrographical surveys using satellite images revealed low temperatures due to upwelling of waters with oxygen deficient. Plankton analysis revealed N. scintillans, Prorocentrum micans and toxic blooms of cyanobacteria Trichodesmium erythraeum (Ehrenberg) (Al Busaidi et al, 2008). More recently, in August 2006, massive fish kills occurred in Muscat.…”

“…Harmful algal blooms (HABs) are caused by microalgae, usually single-celled prokaryotic and eukaryotic photosynthetic organisms that live in freshwater, estuarine and marine realms. Harmful and toxic incidents caused by dinoflagellates are intensifying and spreading all over the world accompanied with extensive ecological damage during the last four decades (Cho, 1981;Olsen et al, 1988;Smayda and Fofonoff, 1989;Chen and Gu, 1993;Hallegraeff, 1993;Nuzziet al, 1996;Anderson, 1997;Wong, 1989;Kim et al,1990Kim et al, , 1993Steidinger, 1993) including the coastal waters of Oman (Thangaraja et al, 1990(Thangaraja et al, , 1991(Thangaraja et al, , 1998(Thangaraja et al, , 2000(Thangaraja et al, , 2007Al Gheilani et al, 2005Al Kindi et al, 2007, unpublished;Al Busaidi et al, 2008;Richlen et al, 2010;Matsouka et al, in preparation). The reasons for the increasing red tides may be related to the global climate change, increase of human impact in coastal zones, awareness resulting from scientific research and reports of HABs events.…”

Characterizing algal blooms in a shallow & a deep channel

“…For example, over 7,000-10,000, 2,500, 100, and 650 tons of fish were killed in Salalah (Oman), Kuwait, Duqm (Oman), Fujairah (UAE: United Arab Emirates) due to the depleted-oxygen waters in 1976, respectively (Al-Gheilani and Matsuoka, 2011Berktay, 2011;Heil et al, 2001;Piontkovski, 2012). Waters colors turned to red, green-orange, yellow-greenish, and brown in 1999, 2008, 2013, 2016 due to the presence of Mesodinium rubrum (Al-Busaidi et al, 2008;Heil et al, 2001), Trichodesmium, Prorocentrum micans, diatoms (not specified) and Noctiluca respectively. Moreover, three membranebased desalination plants were sealed off in Ras Al Khaimah andFujairah in 2008-2009, while Kalbah desalination plant was sealed off in 2013 due to clogging the membrane modules (pore size of 0.0001 -0.001 µm) (Membrane Research Environment (MemRE), 2017) by the algal species whose diameters vary from few to hundreds of microns (Rogers, 2011).…”