Similar to Laolao Bay and Coral Gardens, Barcinas Bay is sheltered from strong winds and large swells which provides calm oceanic conditions throughout much of the year. The protected nature of the bay has allowed thriving reefs to development over the past 5,000 years, resulting in amazing, three dimensional reef structure today (see photo below). This has turned Barcinas Bay into a very desirable destination for divers on Tinian.

One major difference between Laolao and Barcinas Bay is the nature of the freshwater runoff entering the marine system. Similar to Coral Gardens, Barcinas Bay has relatively small amounts of surface water discharge when compared with Laolao Bay, rather, freshwater percolates through the limestone rock as groundwater runoff. Another difference is the lower population on Tinian which helps to explain why fewer water quality violations have occurred over the years in comparison.

The CNMI Marine Monitoring Team has conducted surveys at Barcinan Bay since 2001 with little overall change noted. Coral community evenness, (see Lau Lau Bay for further definations and explanation of evenness and diversity), has changed very little over the years as the persistence of a Porites rus dominated community continues to exist. In fact, Porites is so common that it makes up 90% of all the corals recorded in our benthic video surveys (see benthic coverage graph on right). See the discussion for Coral Gardens to further understand why Porites is so common on these reefs.

Macroinvertebrate abundances have fluctuated over the past 5 years, with a general trend showing grazing urchin populations are decreasing. Grazing creates a clean, desirable reef substrate for coral and other invertebrate settlement (see Talakhaya site for further discussions on grazing and its consequences for reefs). We have noted a small, persistent population of Acanthaster planci or the Crown-of-Thorn starfish (COTS). Studies have found that high nutrient levels lead to enhanced survival for COTS larvae and juveniles. Barcinas Bay is one of many regions where nutrients may be delivered from fresh water runoff, thus helps us to understand why these small, persistent populations may exist. COTS populations have influenced coral community structure on CNMI's coral reefs since their first documentation in the late 1960's. COTS are coral predators that preferably feed on several species of Acroporiid and Faviid corals. Small, persistent populations of COTS may be partially responsible for the Porites dominance at Barcinas Bay.

In contrast to small, persistent populations, scientists are uncertain as to the causes of large, infrequent COTS outbreaks (> 5 COTS per 10 square meters). CNMI-wide, large outbreaks have only been documented in the late 1960's. This outbreak killed up to 90% of the coral community growth in the CNMI (references available upon request). Recovery over the past 40 years differs throughout the CNMI. Reports from the mid 1980's, early 1990's and our data show small, isolated aggregations continuously come and go on many of CNMI's reefs, often associated with freshwater discharge. Many scientists suggest these coral predators may be a natural part of coral reef ecology which allows for new coral communities to develop throughout time. While this may be true we must consider the synergistic effects that upland pollution can have upon a reef following a COTS outbreak. Polluted runoff entering the coastal ecosystem favors the establishement of algal communities instead of corals. See the Talakhaya site to better understand this concept. The result is that a natural COTS outbreak may remove preferred coral prey and replace them with algal communities, never allowing the expected coral community recovery. How a coral reef will recover from large disturbances is a function of many factors including the sites:1) wind and waves exposure, 2) upland pollution levels, and 3) geological foundation, or underwater topography.

What does the future hold for Barcinas Bay? Our data show the majority of recruiting (newly established) corals are massive, encrusting, or Porites species. The low number of branching coral recruits suggests that these reefs will be deviod of Acropora and Pocillopora corals in the future as well as the present. This may be normal given the sites environmental characteristics, however our long term monitoring aims to answer questions like these.

Looking for more indepth information? The marine monitoring program has more detailed information and reports available upon request.