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The intertidal zone of tropical islands is particularly poorly known. In contrast, temperate locations such as California's Monterey Bay are fairly well studied. However, even in these locations, studies have tended to focus on a few species or locations. Here we present the results of the first broadscale surveys of invertebrate, fish and algal species richness from a tropical island, Oahu, Hawaii, and a temperate mainland coast, Central California. Data were gathered through surveys of 10 sites in the early 1970s and again in the mid-1990s in San Mateo and Santa Cruz counties, California, and of nine sites in 2001-2005 on Oahu. Surveys were conducted in a similar manner allowing for a comparison between Oahu and Central California and, for California, a comparison between time periods 24 years apart. We report a previously undocumented richness of intertidal species in both locations: 516 for Oahu and 801 for Central California. Surprisingly, when differences in search efforts are controlled, overall (alpha) diversity appears to be similar between locations, although site level (beta) diversity is much higher in California. Species richness in California generally increased along a wave exposure gradient and distance from an urban area. Much higher numbers of both invasive and endemic species were found on Oahu. In California, more invertebrate species were found in the 1990s, likely due to an improvement in taxonomic resources since the 1970s, and species composition was different in the two surveys due to the high incidence of rare species. Although some southern species increased in number between the two time periods and some northern species decreased, we detected little evidence of change favoring southern or northern species. These results are in line with recent findings that water temperatures in the Monterey Bay have been in a cooling trend since the 1980s, in contrast to many locations elsewhere in the world. [ABSTRACT FROM AUTHOR]

In 1977, Phidiana hiltoni (O'Donoghue in J. Entomol Zool (Pomona College, Claremont, California) 19:77-119, ) began spreading northward from Monterey, California. By 1992, it had reached Duxbury Reef (37° 53′ 23″ N, 122° 41′ 59″ W), 100 km to the north, where other nudibranchs subsequently appeared to decline. The role of P. hiltoni in this decline was investigated through diet analysis, feeding trials, and comparison of historical and recent abundance data. In the wild, P. hiltoni preyed largely on hydroids, but also showed evidence of predation on nudibranchs. In the laboratory, P. hiltoni attacked most of the dendronotid and aeolid nudibranchs presented to it, ingesting small individuals whole. The pooled abundance of nudibranchs vulnerable to attack by P. hiltoni declined an average of two-thirds at Duxbury Reef since its arrival, compared to (1) no change in the non-vulnerable species and (2) no change in either group at two other sites where P. hiltoni was one to two orders of magnitude less abundant. Phidiana hiltoni therefore appears to have caused this decline, likely through a combination of direct predation and competition for prey. A brief larval period, combined with cyclonic re-circulation in the lee of Point Reyes, may be driving self-recruitment of P. hiltoni at Duxbury Reef, as well as hindering further northward spread. [ABSTRACT FROM AUTHOR]

Abstract: Marine protected areas ( MPAs) designed to provide harvest refugia for red sea urchins ( Strongylocentrotus franciscanus) offer a unique opportunity to study the indirect effects of urchin fishing on subtidal communities. Sea urchins may provide important cryptic microhabitat for juvenile abalone sheltering beneath urchin spines in shallow habitats worldwide. We investigated the abundance of juvenile (3–90 mm) red abalone, ( Haliotis rufescens) and the rare flat (<90 mm) abalone ( H. walallensis) on protected and fished rocky reefs in California. Abalone abundance surveys were conducted inside 24 × 30 m plots on three protected reefs with red sea urchins present and three fished reefs where red sea urchins were removed by commercial or experimental fishing. Significantly more juvenile abalone were found in 1996 and 1997 on protected reefs with urchins present than on fished reefs ( χ 2 = 188, df = 1, p < 0.001). Juvenile red abalone abundance was not correlated with local adult red abalone abundance or habitat rugosity. One-third of the juveniles inside the MPAs were found under the urchins' spine canopy, as were a suite of unfished marine organisms. In the laboratory, juvenile abalone survived better ( χ 2 = 7.31, df = 1, p < 0.01) in crab predation experiments in which red sea urchins were available as shelter. Fishing red urchins reduced structural complexity, potentially decreasing microhabitat available for juvenile abalone. This example demonstrates how MPAs designed for one fished species may help other species, illustrating their usefulness for ecosystem-based fishery management and marine conservation. [ABSTRACT FROM AUTHOR]

More non-native species (NNS) are reported from harbors, estuaries and protected embayments than in wave-exposed, open-coast habitats. In California (USA), hundreds of NNS have become established in international ports, and dozens are known from smaller estuaries. In contrast, only 22 NNS are reported from the state’s 1350 km of open coast. As a result, the perception that open-coast habitats are not vulnerable to invasions has persisted. Management and monitoring focuses on ports and estuaries; the last major monitoring effort on the open coast occurred in 2004. Much of the species-rich Central California coast is now part of a network of marine protected areas (MPAs). We surveyed 12 wave-swept rocky intertidal and eight subtidal sites (from 37°53′40N 122°42′30W to 36°31′16N 121°56′22W) for NNS. At least one NNS was detected at half of the sites surveyed, but most were not widespread or abundant. One exception, a bryozoan in the Watersipora spp. complex, known primarily from ports and estuaries, was found at multiple sites, and was abundant at some. Another non-native, the alga Caulacanthus ustulatus, was abundant at a single site. MPAs were just as likely as sites outside of MPAs to have NNS. For subtidal sites, proximity to a harbor was correlated with the abundance of non-natives. Our findings suggest that our study area is still relatively uninvaded, but the success of Watersipora within some of these highly diverse rocky shore sites underscores the potential vulnerability of high-value open-coast systems to invasions. [ABSTRACT FROM AUTHOR]