Problems Without Passports: Scientific Research Diving at USC Dornsife--Contrasting Reef Ecosystems in Guam

Mareika Vandeveer and Justin Bogda - 

After ten days of training on Catalina off the coast of Southern California in poor visibility and cold water, it was our privilege that this site was our first experience of tropical SCUBA diving.

With mounds of coral forming castle-shaped forests all around, we had truly entered a new world that exceeded our wildest expectations. Double Reef had amazing visibility, and we saw a great diversity of invertebrates, fish and coral species.

At each dive site, we record the number of specific invertebrates present and substrate type along a 100-meter belt transect. These include sea cucumbers, sea urchins, spider conchs and giant clams.

These species, with enough data, can hopefully tell us the diversity and health of the specified reef ecosystem, and with enough data over enough time, tell us how the reefs are being affected by anthropogenic factors.

The next day we dove in Apra Harbor on Western Shoals, a reef that will be potentially impacted by the proposed Department of Defense buildup. In contrast to Double Reef, this site is in the heart of Apra Harbor, a populated area surrounded by development of both commercial and military complexes.

Though we did not see as many invertebrates and reef fish as we did in Double Reef, the coral coverage and size was remarkable considering its location. We also saw an elephant ear sponge, a species common in Apra Harbor, but perhaps in no other place on Guam. Western Shoals seemed like an oasis among all of the surrounding development.

But this could all soon change. As part of the Department of Defense buildup, a large part of Apra Harbor must be dredged to base an aircraft carrier. This dredging would not only physically destroy coral reefs, but also indirectly impact surrounding ecosystems with sedimentation.

While the Department of Defense uses silt nets to prevent such sedimentation, it has been known to be ineffective, and the sediment in Apra Harbor is so fine that once it becomes re-suspended in the water column it will remain there for a very long time. This sedimentation reduces the amount of sunlight available to coral’s photosynthetic process, and thus adversely affects the entire ecosystem.

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