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The intertidal zone is a unique marine environment that is covered with water during high tide and exposed to air during low tide. This includes tidepools and the area of the shore that receives splash from waves. The assemblage of algae and animals that live there is often very unique and adapted for a challenging set of living conditions that come with the partial exposure. The intertidal is an important ecosystem for gaining information about ecological interactions between organisms and one another as well as with the physical environment. Some of the most important scientific theories of the 20th century began with intertidal research.

Exposed at low tide, the intertidal zone is one of the most accessible marine ecosystems. The same easy accessibility that makes this zone especially susceptible to human impacts also makes it ideal for a school or community action project. Well-studied in temperate regions, the intertidal zone has been nearly ignored in Hawaii in the past few decades, to the point that some researchers doubt its existence as a distinct zone. Research neglect may be due to the subtlety of Hawaii’s intertidal zone. The tidal range is small - about 1 meter between extreme low and high tides. The biomass of plants and animals is also significantly lower than in most temperate intertidal zones, although the diversity of Hawaii’s intertidal invertebrates is probably comparable to that of the highly speciose Monterey Bay California. Whatever the reasons, the Hawaiian intertidal has received little scientific study as an ecosystem, and even less conservation attention.

Concerns about the disappearance of edible algae species at an intertidal bench in Ewa Beach on Oahu’s Leeward Side have highlighted one way in which the intertidal zone is vulnerable. Additionally, Oahu’s intertidal zone appears to be highly invaded relative at least to the West Coast of the US (Zabin et al, in prep). Our research indicates that 9 percent of algae species and 11 percent of invertebrates are either non-native or cryptogenic. While many of the invaders have been found at one site (Coconut Island on Windward Oahu), several have become widespread and are frequently among the most abundant organisms at a given site. If predation and herbivory are lower in intertidal areas than adjacent reefs, invasive species may flourish. There has been virtually no research on the impacts of these invaders on intertidal communities or on effective removal techniques. At the very least, monitoring efforts for invasive species must address the intertidal zone as well as harbors and coral reefs.

Importance of monitoring Hawaii’s Intertidal

Monitoring is the process of tracking organisms over time. Students involved in OPIHI will be monitoring the abundances of key species through the use of consistent procedures, establishing a baseline from which changes in species composition can be measured. As data accumulates over time, natural or human driven changes such as global warming, trampling, pollution, and introduction of invasive species can be identified and measured. Resource managers and scientists can use this data for decision making purposes.
OPIHI: Our Project in Hawaii's Interdental - Contact: philippo@hawaii.edu