DMWR probes red tide algae bloom in Pago Harbor
Over the past few weeks, the water in the Pago Pago Harbor has been changing colors, from dark brown and tan to a faded olive green and then back to brown again. The discoloration, coupled with inquiries from the general public, sparked action by the Department of Marine and Wildlife Resources (DMWR) whose biologists took water samples from the area this past Wednesday.
DMWR Deputy Director Selaina Vaitautolu-Tuimavave told Samoa News yesterday the samples are being sent off island for testing and the results will be expected soon. “We don’t have the facilities here on island to conduct testing locally,” she said.
Simple water quality testing kits were used to sample the water for nitrate and phosphate. Samples were taken from 12 different sites around the inner, middle and outer harbor.
According to a media release from DMWR fisheries biologist Alice Lawrence, microscopic examination revealed the abundant presence of a single-cell organism.
A photograph was sent to Dr. Steve Morton, head of the Marine Biotoxins program based in Charleston, South Carolina who identified it as Prorocentrum micans — a dinoflagellate, a type of plankton or tiny marine algae that is known to form large blooms.
“Studies have shown that a large bloom of this species usually occurs with a combination of high levels of phosphate and slow water movement,” Lawrence wrote, adding the color of the water is usually a brown red at the beginning, followed by a black brown color at the final stages of the bloom, which is similar to what is happening in the inner harbor area.
“__Experimental tests in China showed that a bloom can kill shellfish populations; however, it is usually considered harmless to other organisms at higher levels of the food chain,” Lawrence continued. “Indirect effects to the marine environment can be caused when the algae die and decompose which uses up the oxygen in the water, causing fish and other animals to leave the area or die.”
Lawrence said there is no evidence of this species’ impact on humans; however, other species of dinoflagellates have been found to produce irritants that can cause severe respiratory irritation and severe contact dermatitis which result in large, burning, and itchy rashes on the skin.
According to Lawrence, initial results indicated negative levels for nitrate (0 mg/l), but an excessively high level of phosphate (2 – 4 mg/l) in the samples taken from the mid-harbor to the inner harbor area.
Section 24.0205(m) of the American Samoa Water Quality Standards provide that total phosphorus shall not exceed 0.0300 mg/l in Pago Pago Harbor.
“Phosphorous, like nitrogen, is an essential nutrient for the plants and animals that make up the aquatic food chain. However, even a small increase in phosphorous can trigger faster plant growth, algal blooms, low dissolved oxygen, and create unlivable conditions for certain fish, invertebrates, and other creatures.”
Phosphorous is introduced into the environment by human activities like human and animal wastes, fertilizers, industrial wastes, and human disturbance of the land and its vegetation, Lawrence said.
The most recent algal blooms in the territory were recorded in 2007 and 2009 in the Pago Pago Harbor, which Dr. Morton ascribed to the dinoflagellate Ceratium furca.
Those algal blooms, according to Lawrence, were thought to be caused by an excess of nitrogen fertilizer from an unconfirmed source near the harbor head. She said the red tide disappeared when nitrogen levels in the harbor disappeared. Investigation will need to be carried out to determine the current cause of excess phosphates in Pago Pago Harbor, “which is likely to be different from the algal blooms in the past.”
Lawrence said there is reason to believe that a specific pollution incident may have caused this bloom, potentially as far back as the end of August.
“A fish was seen swimming erratically upside down in the inner harbor area on August 22 and was later found dead and brought to the DMWR office,” she said. The fish was 45cm long and identified as Plectropomus maculates, a spotted coral grouper or Gatala. Tissue samples were sent to the Center for Disease Control in Hawaii and the results are still pending.
Lawrence said recent discussions with harbor users have resulted in reports of a school of Mullet (or Agae) also swimming upside down near the DMWR marina dock. Additionally, reports of public health problems have arisen, including children swimming near the marina complaining of boils on their skin, and DMWR divers reporting ear and respiratory problems after being in the water near Aua in September. Also, a DMWR employee who was out on a jet ski to get samples Wednesday now has red itchy boils on his arm where he got splashed by the water.
“They said they also saw a fish come up to the surface and swim upside down!” Lawrence reported.
Until further notice, the DMWR recommends the public stop swimming and fishing in the harbor area.