Ick! Why Is There So Much Algae On The Reef?

There's always time for a selfie, even underwater.

There's always time for a selfie, even underwater.


When  MMES  candidate Tanya Ramseyer discusses the marine research she is engaged in at the  University of the Virgin Islands, she becomes intense and passionate. In her second year in the masters program at  CMES, Tanya is deeply focused on algae. The excitement she brings to her research is infectious and refreshing. 

Dictyota spp .  is found in abundance on reefs around the USVI.

Dictyota spp.  is found in abundance on reefs around the USVI.

Dictyota  spp.  is the brown macroalgae you will see in abundance on reefs around the USVI. It is super fast growing and reproduces asexually so each fragment can grow independently. If you’ve been snorkeling lately, you will see  Dictyota  overtaking coral reefs everywhere. This macroalgae can kill coral by abrading its sensitive surfaces, shading it from the sun and even by transferring diseases. Tanya is investigating why this particular macroalgae has become so dominant and what, if anything, can be done to quell its growth. 


One hypothesis for the algae’s rapid growth is that it is caused by the high degree of runoff seen on our shorelines. An experiment Tanya is conducting  is designed to tell us if runoff is in fact the cause (theoretically by fertilizing the algae)  of its overgrowth. 

Tanya created “exclusion cages” with 2.5 cm fencing to isolate patches of Dictyota  from herbivore activity (fish grazing).  She then fertilized the algae in much the same way you fertilize a lawn. The thinking is that algae would flourish, as grass does when fertilized, but in fact the opposite was true. There was a decrease in algal height and biomass.  This discovery leads to a plethora of additional questions: “Was too much fertilizer used?”, “Should the cages be made of plastic (thus avoiding potential leaching of metals from the fencing)?”, “Is the water already over-fertilized?” 

Tanya’s field research is currently in its third series of testing before a determination can be posed, but one fact is clear: this is not an equal playing field!  Dictyota  can reproduce constantly and quickly. Corals on the other hand reproduce just once a year and are extremely slow growing. The problem is compounded by the fact that reef herbivores such as the parrotfish have been fished to a lower abundance. (Other marine herbivores such as sea urchins and crabs eat algae too, but large parrotfish were the primary herbivore). 

Tanya prefers to spend her time engaged in field research, as seen here. 

Tanya prefers to spend her time engaged in field research, as seen here. 

Tanya came to UVI after earning her undergraduate degree in biology at Old Dominion University in Virginia. She fell in love with UVI's unparalleled location, but also because after conferencing with Dr. Tyler Smith by phone, it was clear that their goals were aligned. Another bonus is that UVI is one of the few universities that offers a technical diving program. Technical diving goes beyond the scope of recreational diving and is sometimes used as a way to participate in extreme adventure diving. For UVI's  purposes however, it is incredibly helpful in research diving. 

When not in the field, Tanya takes her work to the hammock. 

When not in the field, Tanya takes her work to the hammock. 

“Dr. Smith is super involved and is always willing to assist in field work. He even came out to multiple research sites with rebreathers to assist in setting up the experiments.”  Rebreathers allow divers to remain underwater for up to 4 hours and is an even more highly specialized level of certification. Tanya also participates in technical (decompression) diving and has used these practices to work at her deeper research sites. 


Interestingly, although women are a minority in science, the marine science program here at UVI has considerably more female students than male. Tanya notes that a few years ago she very nearly missed out on the opportunity to participate in a competitive internship because the women’s dorms were full. It was much smaller than the men’s dorms. While there is a shift taking place in women’s participation in science, many programs have not caught up yet. When you consider that more women than men are seen at science conferences and in classrooms, that dichotomy was interesting and exciting for her to experience. 

Tanya looks forward to earning her Masters in Marine and Environmental Studies in December of this year.