Cayman’s increasing population isn’t causing pressures only on land. The country’s distinctive crystal-clear waters and reefs are imperiled unless nutrients feeding harmful algae blooms are reduced, a scientist has warned.

According to comments prepared for the Cayman Islands Department of Environment by marine scientist Thomas Goreau, president of the Global Coral Reef Alliance, those increased nutrient sources risk tipping the reefs into being totally overrun by invasive algae, which has already happened in almost all tourism areas across the Caribbean.

According to Goreau, the sources of nutrients feeding harmful algae blooms in Cayman waters include “septic tanks, the sewage plant – which only treats a tiny portion of the sewage the islands produce, and does not treat them to tertiary level to remove nutrients – the garbage dump, the dolphinarium, the turtle farm, stingray and tarpon fish feeding, golf courses, garden and lawn fertilizers”.

“Cayman lacks nutrient water quality standards that protect the health of coral reefs, seagrasses, and mangroves,” Goreau wrote.

Recommendations

In the paper Goreau prepared for the Cayman Islands government, he said the Turks and Caicos Islands has now proposed adopting water quality standards that protect their coral reefs

“New technology exists to allow continuous real time mapping of nutrients, identify every source, and track each to its origin,” he wrote.

“Such instruments are now available that are portable, battery operated, can be deployed from small boats.”

He recommended the Cayman Islands government establish coral-reef-specific water quality standards and establish a nutrient measuring laboratory to map changes in nutrients in Cayman coastal waters on seasonal, extreme event and long-term scales.

Department of Environment Deputy Director Tim Austin said the department’s research team met with Goreau and discussed water-quality issues and the inherent difficulties of measuring the low levels of nutrients that are still harmful to coral reefs and seagrasses.

“We are currently involved in multiple projects that are looking towards reestablishing the DOE’s Water Quality Programme that ran for many years and then had to be put on hold due to resource issues. This report will help to evaluate the various options that are being investigated,” he said.

No Northwest Point sewage system expansion

In particular, septic systems represent well over 70% of wastewater disposal, and septic tanks are used along the Northwest Point in West Bay, where three large scale construction projects are currently underway.

There are concerns that nutrients leaching into the sea could affect some of the most accessible and beautiful coral reefs in the Cayman Islands, which are located immediately offshore along the Northwest Point Road – including dive sites like Trinity Caves and Bonnie’s Arch.

In response to questions from the Compass, the director of Water Authority-Cayman, Gelia Frederick-van Genderen, said, “At this stage, the Water Authority has no short- or medium-term plans for expansion of the public sewerage system into the Northwest Point Road area.”

The public sewage system in Grand Cayman was first established in 1987, with the initial focus being for treatment of wastewater from the properties on, or adjacent to, West Bay Road.

One of the duties of the Water Authority is to provide for the collection, treatment and disposal of sewage (wastewater) in a manner that is safe, efficient, and affordable.

“Financial constraints dictated that priority was initially given to the more densely developed areas between Public Beach and George Town cemetery,” explained Frederick-van Genderen.

She added that, over the last 35 years, significant new commercial developments, as well as additional residential areas, have been connected to the public sewage system, including Crystal Harbour and Camana Bay.

The Water Authority director added that the main sewage system has now been extended north to the Renaissance development on West Bay Road, and the Water Authority “has committed to extending the public sewage system along West Bay Road to accommodate the proposed multi-story development just south of Marsh Road”.

Not a new problem

Catherine Crabb, a scientist from Water Authority-Cayman’s department of water resources and quality control, noted in a paper in 2009 that, “Approximately 20% of wastewater generated in the Cayman Islands is collected and treated at the central wastewater treatment plant operated by the Water Authority; the remaining 80% is treated in onsite treatment systems” – referring to septic tanks and anaerobic treatment units.

Crabb added, “For years, onsite treatment systems were seen as temporary installations to be replaced by a central system. As a result, onsite systems were subject to limited oversight by regulatory agencies.”

A previous study looking at the leaching of nutrients into the waters in Florida, published in the Marine Pollution Bulletin, indicates that effluent from septic systems can pollute groundwater and surface waters in coastal waters. The authors of the study claim that the research “demonstrates the need to reduce reliance on septic systems in urbanized coastal communities, to improve water quality and subsequently mitigate harmful algal blooms”.

In another scientific paper published in 2014, scientists, including Goreau, said, “The growth rate of algae, like all plants, is fundamentally limited by available nitrogen and phosphorous.

“When these critical nutrient elements increase, they serve as fertilizers, promoting rapid growth of the weeds able to take them up fastest. These weeds smother all the other organisms in the ecosystem, causing catastrophic crashes of biodiversity and of economically valuable living resources such as coral reefs, fish and shellfish.”

The US National Oceanic and Atmospheric Administration previously noted that there is a strong consensus in the scientific community that there needs to be a “better understanding the problem of nutrient pollution of coastal waters”.

“The degradation of coastal marine ecosystems by nutrient pollution is keenly felt by the public in many regions, and society is increasingly striving to reverse coastal nutrient pollution,” the agency said.

For more information on water pollution in Grand Cayman please see the report referred to in the article: