Chela J. Zabin

A case study of project‐based instruction in the ninth grade: a semester‐long study of intertidal biodiversity

In this descriptive case study, project‐based learning is presented as a teaching model that combines elements from other learning strategies. High school students participating in an intertidal monitoring project built around this model increased their content knowledge related to the ecology of the intertidal zone and improved their scientific investigation skills. Several aspects of project‐based instruction are considered critical to success. Projects grounded in authentic scientific research develop scientific investigation skills through real world application. Alignment of scientific and educational goals enhances learning when the project is conducted in a sound pedagogical manner while maintaining scientific authenticity. Student teamwork builds a scientific community and makes the work more manageable. One of the most critical elements for success is a long‐term commitment to project activities with connections between the project and related curricular topics. Flexibility of the school curriculum enables required content to be connected to the project’s thematic base. These connections provide students with a common knowledge foundation and make it easier for educators to build such projects into their curricula.

Testing local and global stressor impacts on a coastal foundation species using an ecologically realistic framework

Despite the abundance of literature on organismal responses to multiple environmental stressors, most studies have not matched the timing of experimental manipulations with the temporal pattern of stressors in nature. We test the interactive effects of diel-cycling hypoxia with both warming and decreased salinities using ecologically realistic exposures. Surprisingly, we found no evidence of negative synergistic effects on Olympia oyster growth; rather, we found only additive and opposing effects of hypoxia (detrimental) and warming (beneficial). We suspect that diel-cycling provided a temporal refuge that allowed physiological compensation. We also tested for latent effects of warming and hypoxia to low-salinity tolerance using a seasonal delay between stressor events. However, we did not find a latent effect, rather a threshold survival response to low salinity that was independent of early life-history exposure to warming or hypoxia. The absence of synergism is likely the result of stressor treatments that mirror the natural timing of environmental stressors. We provide environmental context for laboratory experimental data by examining field time series environmental data from four North American west coast estuaries and find heterogeneous environmental signals that characterize each estuary, suggesting that the potential stressor exposure to oysters will drastically differ over moderate spatial scales. This heterogeneity implies that efforts to conserve and restore oysters will require an adaptive approach that incorporates knowledge of local conditions. We conclude that studies of multiple environmental stressors can be greatly improved by integrating ecologically realistic exposure and timing of stressors found in nature with organismal life-history traits.

Oyster Shells as Vectors for Exotic Organisms

ABSTRACT Oyster shell may be taken from one bay and placed in another for a variety of purposes, including the restoration or enhancement of native oysters or other native species. Whereas it is generally appreciated that undesirable organisms can be transferred with live oysters, oyster shells alone can also serve as vectors for the accidental introduction of marine organisms to new locations. We here describe oyster shell plantings made for various purposes, the potential for these plantings to inadvertently transfer live organisms, and biosanitary procedures that could limit these transfers.

Aquaculture as a vector for marine invasions in California

Although ballast water and hull fouling are widely recognized as important vectors for marine invasions, the risk posed by commercial aquaculture remains poorly quantified. To understand the importance of aquaculture as an invasion vector in California, we conducted an analysis of both current and historical introductions of marine and estuarine species associated with aquaculture using a comprehensive database (‘NEMESIS’) and permitting records for species imported into California. Our results showed that 126 non-native species associated with commercial aquaculture have been reported from California waters and 106 of these have become established. The vast majority are unintentional introductions linked to historical importation practices of the aquaculture industry. To understand the consequences of these invasions, we reviewed the literature on the impacts of mollusk and algal species introduced into California via aquaculture. Of the few studies we found, the majority demonstrated negative impacts on native species. Finally and significantly, we found that changes in aquaculture importation practices over the past decade have resulted in most shellfish currently being imported as larvae or juveniles. Consequently, rates of unintentional introductions have been reduced. We cautiously conclude that current aquaculture importation in California represents a minor risk as a vector for introductions of NIS.

Do locals rule? Interactions between native intertidal animals and a Caribbean barnacle in Hawai'i

Chthamalus proteus, a high intertidal barnacle from the Gulf of Mexico and the Caribbean, is one of the most conspicuous recent introductions to Hawaiian waters. It arrived sometime between the early 1970s, when the last thorough survey of intertidal barnacles on O‘ahu was done (Matsuda 1973), and the late 1990s, when it was photographed by an amateur biologist who was putting together a book on Hawai‘i’s sea creatures (Southward et al. 1998). On O‘ahu, the barnacle attains high densities in protected bays and lagoons, particularly where there are few other intertidal organisms. Chthamalus proteus is somewhat less abundant in semiprotected waters where it co-occurs with a suite of native organisms. We examined interactions between C. proteus and two native Hawaiian species, the barnacle Nesochthamalus intertextus and the pulmonate limpet Siphonaria normalis. The native barnacle is highly abundant on seawalls in Waikiki and frequently overgrows or undercuts the invader. Nesochthamalus intertextus grows twice as fast as C. proteus, which may allow the native to compete more effectively for space. To examine whether the native barnacle is limiting the distribution of the invader, we established 20 permanent quadrats along a seawall. In half of the quadrats native barnacles within 5 mm of invasive barnacles were removed; the remaining quadrats served as controls. Growth and survivorship of invasive barnacles in the quadrats have been tracked for 1 yr. An additional 12 quadrats were cleared of all native intertidal organisms. Recruitment of C. proteus to these quadrats and to 12 control quadrats was recorded for 10 months. Invasive barnacles in the treatment quadrats grew faster than those in control plots. Neither recruitment nor mortality was significantly different in treatment versus control plots, however, suggesting that factors other than competition (such as larval supply) also play a role in the distribution of the invader. It is more usual to ask whether an invader is impacting a native. There were too few of the invasive barnacles at Waikiki to test this with any statistical power. At Kualoa Beach, on O‘ahu’s windward side, the situation is reversed: the invader is abundant and the native is relatively rare. An experiment similar to the one in Waikiki was established in March 2000 to test the effect of C. proteus on the growth, mortality, and recruitment of N. intertextus. After 1 yr, there appeared to be no effect of the invader on the native in any of these categories. Interactions in Kāne‘ohe Bay between C. proteus and the pulmonate limpet S. normalis were also examined. The pulmonates are highly abundant (mean 30/100 cm) at Coconut Island on a seawall that is composed of several rock types. A survey of the wall showed that the invasive barnacles were less abundant on light-colored rock and that there was an additional negative effect of pulmonate density on barnacle abundance. The pulmonates were more abundant on light-colored rock; their densities were not additionally affected by barnacle numbers. Four types of cement settlement panels (dark smooth, dark rough, light smooth, light rough) were placed in the intertidal to test for settlement preferences of C. proteus and S. normalis. Barnacles did not show a preference for color, but limpets recruited preferentially to light-colored panels. Further experiments examining the effect of the pulmonates on recruitment of C.