Select Language :   فارسی
Home  |   Links   |      Contact Us 
 

 

Red Tide in the Persian Gulf and the Gulf of Oman

Red tide is a naturally occurring, higher than normal concentration of microscopic, single celled, photosynthetic algae. The coastal waters of the Persian Gulf and the Sea of Oman host many indigenous species of marine algae whose populations are greatly influenced by water quality (e.g., levels of salinity, dissolved oxygen, nutrients, and minerals). Changing water quality can trigger rapid growth in certain algal populations. These algal ‘‘blooms’’ (commonly referred to as harmful algal blooms or HABs) occur naturally along the Persian Gulf and the Sea of Oman.

Beside collaborative studies on Red Tide between Iranian National Institute for Oceanography and Atmospheric Science (INIOAS), Hormuzgan University, and Prof. Dr. K. Matsuoka of Nagazaki University, routine daily recording of satellite data (MODIS Aqua) is being carried out by INIOAS.

The occurrences of phytoplankton blooms are a regular phenomenon in the coastal waters of the Oman Sea and the Persian Gulf (Thangaraja et al. 2007). Recent occurrence of Red Tide in the Persian Gulf and the Sea of Oman was linked to Cochlodinium polykrikoides Margalef. This is an armored harmful dinoflagellate, which appeared first in the Oman Sea and the Persian Gulf (Fig.1) and lasted from August 2008 to late August 2009. In Iran, several red-brown patches of several kilometers were observed, extending from Sirik Port in the Sea of Oman to Bushehr in the central Persian Gulf, covering an estimated distance of approximately 750 km. The dinoflagellate Cochlodinium polykrikoides bloom was responsible for water discoloration and the heavy fish mortality (mainly shallow water fish) along the Persian Gulf and the Sea of Oman and caused panic in local population. C. polykrikoides (Fig. 2) is a cyst-forming species that recurred in this area with abundance ranging from 0.5-1.0 x 103 to 52.0 x 106 /cells l-1 and with a high biomass expressed in terms of chlorophyll-a, ranging from 0.6 to 62.6 mg/m3. The blooms were observed with a seawater temperature range of 22.27- 25.23 °C. In addition, coral reefs at Qeshm and Larak Islands in the eastern part of the Persian Gulf were also affected. In the third half of 2008, mass mortality of reef fishes and invertebrates, especially reef corals, occurred during blooms of the dinoflagellates C.ploykricoides. Large-scale mass-mortalities of various benthic organisms were accompanied by red tides of this species.

On the basis of field observations, percentage cover of coral damages varied from one Island to another; at Qeshm Island, up to 90% coral mortality occurred with massive poritids most severely affected, whereas at Larak Island, approximately 30% of branching acroporid mortality (Fig. 3) occurred and this was confined to the shallow reefs. These blooms have interfered with recovery of reefs disturbed during the 1996/1998 warming events. Cochlodinium polykrikoides Margalef, an armored harmful dinoflagellate, appeared first in the Oman Sea and the Persian Gulf, caused fish and shellfish mass mortalities. C. polyrkikoides occurring in the Oman Sea and the Persian Gulf belongs to the American/Malaysian ribo-type, which is distributed worldwide (Fig. 4). It is concluded that this phenomenon did not occur due to oxygen radicals, but mainly due to polysaccharides.

 

Fig.1. Direction of the red tide of Cochlodinium polykrikoides in the Oman Sea and

the Persian Gulf in 2008-2009. Arrows indicate the current direction in the Oman

Sea and the Persian Gulf.  

 


 

Fig.2. Photomicrographs of Cochlodinium polykricoides.

 

 

 

Fig. 3. Damages to various marine organisms caused by red tides of Cochlodinium polykrikoides. 1: Mass mortality of fish and other benthic organisms near Qeshm Island on 2008. 2 and 4: Mass mortality of cultured Goldlined Sea breams in Oman on 23 Nov. 2008. 3. Damaged branching corals in north of Larak Island (after Matsuoka et al., 2010).

 

                                              


 

Fig. 4. Geographical Distribution of Cochlodinium polykrikoides with emphasis on

three ribo-types. The American/Malaysian ribo-type showing the widest distribution.

 

 

Red Tide in the Persian Gulf and the Gulf of Oman

Red tide is a naturally occurring, higher than normal concentration of microscopic, single celled, photosynthetic algae. The coastal waters of the Persian Gulf and the Sea of Oman host many indigenous species of marine algae whose populations are greatly influenced by water quality (e.g., levels of salinity, dissolved oxygen, nutrients, and minerals). Changing water quality can trigger rapid growth in certain algal populations. These algal ‘‘blooms’’ (commonly referred to as harmful algal blooms or HABs) occur naturally along the Persian Gulf and the Sea of Oman.

Beside collaborative studies on Red Tide between Iranian National Institute for Oceanography and Atmospheric Science (INIOAS), Hormuzgan University, and Prof. Dr. K. Matsuoka of Nagazaki University, routine daily recording of satellite data (MODIS Aqua) is being carried out by INIOAS.

The occurrences of phytoplankton blooms are a regular phenomenon in the coastal waters of the Oman Sea and the Persian Gulf (Thangaraja et al. 2007). Recent occurrence of Red Tide in the Persian Gulf and the Sea of Oman was linked to Cochlodinium polykrikoides Margalef. This is an armored harmful dinoflagellate, which appeared first in the Oman Sea and the Persian Gulf (Fig.1) and lasted from August 2008 to late August 2009. In Iran, several red-brown patches of several kilometers were observed, extending from Sirik Port in the Sea of Oman to Bushehr in the central Persian Gulf, covering an estimated distance of approximately 750 km. The dinoflagellate Cochlodinium polykrikoides bloom was responsible for water discoloration and the heavy fish mortality (mainly shallow water fish) along the Persian Gulf and the Sea of Oman and caused panic in local population. C. polykrikoides (Fig. 2) is a cyst-forming species that recurred in this area with abundance ranging from 0.5-1.0 x 103 to 52.0 x 106 /cells l-1 and with a high biomass expressed in terms of chlorophyll-a, ranging from 0.6 to 62.6 mg/m3. The blooms were observed with a seawater temperature range of 22.27- 25.23 °C. In addition, coral reefs at Qeshm and Larak Islands in the eastern part of the Persian Gulf were also affected. In the third half of 2008, mass mortality of reef fishes and invertebrates, especially reef corals, occurred during blooms of the dinoflagellates C.ploykricoides. Large-scale mass-mortalities of various benthic organisms were accompanied by red tides of this species.

On the basis of field observations, percentage cover of coral damages varied from one Island to another; at Qeshm Island, up to 90% coral mortality occurred with massive poritids most severely affected, whereas at Larak Island, approximately 30% of branching acroporid mortality (Fig. 3) occurred and this was confined to the shallow reefs. These blooms have interfered with recovery of reefs disturbed during the 1996/1998 warming events. Cochlodinium polykrikoides Margalef, an armored harmful dinoflagellate, appeared first in the Oman Sea and the Persian Gulf, caused fish and shellfish mass mortalities. C. polyrkikoides occurring in the Oman Sea and the Persian Gulf belongs to the American/Malaysian ribo-type, which is distributed worldwide (Fig. 4). It is concluded that this phenomenon did not occur due to oxygen radicals, but mainly due to polysaccharides.

 

Fig.1. Direction of the red tide of Cochlodinium polykrikoides in the Oman Sea and

the Persian Gulf in 2008-2009. Arrows indicate the current direction in the Oman

Sea and the Persian Gulf.  

 


 

Fig.2. Photomicrographs of Cochlodinium polykricoides.

 

 

 

Fig. 3. Damages to various marine organisms caused by red tides of Cochlodinium polykrikoides. 1: Mass mortality of fish and other benthic organisms near Qeshm Island on 2008. 2 and 4: Mass mortality of cultured Goldlined Sea breams in Oman on 23 Nov. 2008. 3. Damaged branching corals in north of Larak Island (after Matsuoka et al., 2010).

 

                                              


 

Fig. 4. Geographical Distribution of Cochlodinium polykrikoides with emphasis on

three ribo-types. The American/Malaysian ribo-type showing the widest distribution.

 

All rights reserved to the Iranian National Institute for Oceanography and Atmospheric Science.
Portal Design and Optimization (SEO) : Raahbar