ABSTRACT An Analysis Of Human Disturbance To Rocky Intertidal Communities Of San Luis Obispo County Grant Tyler Waltz The number of coastal areas open to public access in California and San Luis Obispo County is increasing due to the acquisition by California State Parks of land previously owned by private entities. For example, California State Parks acquired property from the Hearst Corporation in 2005, which included 18 miles of coastline. California State Parks is responsible for providing public access in these newly acquired areas and also for maintaining the health of the natural systems found on these properties. Part of the California State Parks’ strategic vision maintains that they seek to consider the impacts of every decision they make on the next seven generations of Californians. To balance the competing demand of providing access with long-term sustainability, State Parks managers require sound scientific data to evaluate the impacts of human access to the ecosystems they manage. One ecosystem susceptible to human access in these new State Park areas and in other areas throughout the state is the rocky intertidal (e.g. Beauchamp and Gowing 1982, Ghazanshahi et al. 1983, Hockey and Bosman 1986, Povey and Keough 1991, Addessi 1994, Fletcher and Frid 1996, Brown and Taylor 1999, Murray et al. 1999, Van De Werfhorst and Pearse 2007). This thesis represents a collaborative effort between State Parks Managers scientists at California Polytechnic State University San Luis Obispo, and scientists at Tenera Environmental Inc. to provide sound scientific data on the impacts of visitors to rocky intertidal biological communities in San Luis Obispo County. A three-pronged approach was used to assess the effect of visitors to rocky intertidal communities: 1) an observational study to quantify visitor densities in publicly accessible rocky intertidal communities, 2) an experimental manipulation of visitor density to rocky intertidal communities based on the visitor densities observed in part 1 and used to identify organisms susceptible to foot traffic (access-indicator taxa), and 3) an observational study of publicly accessible rocky intertidal sites exposed to levels of foot traffic shown to cause declines in access-indicator taxa from part 2. I was involved with all three portions of the study and my thesis is focused on presenting and discussing parts 1 and 3 in detail. Visitor counts and the observational access-indicator taxa study (parts 1 and 3) were conducted in Montaña de Oro State Park (MDO) in San Luis Obispo County from 2007-2009. There was abundant accessible rocky intertidal coastline in the park. Three popular rocky intertidal sites were chosen within the park to conduct visitor counts. Visitors were quantified from fixed locations on the bluff above each of the three observation sites on sixteen occasions during the course of three years. These counts were used to estimate the annual number of visitors to each site. The area of each intertidal observation site was also calculated and with the annual number of visitors, was used to calculate the annual density of visitors to the rocky intertidal at each site. This represents a novel approach to quantifying visitor numbers to rocky intertidal communities. Additionally, I examined whether there was a relationship between the number of cars entering the park and the density of rocky intertidal visitors or between the number of cars parked at each site and the density of rocky intertidal visitors. The annual density of visitors at one of the observation sites in MDO, Hazard Reef, was shown to be approximately equal to the moderate treatment level from the experimental study (part 2). This moderate level of visitor density was shown to significantly reduce the abundance of five rocky intertidal taxa: rockweed (Silvetia compressa, Hesperophycus californicus, and Fucus gardneri), Endocladia muricata, Mastocarpus papillatus, limpets, and chitons. To assess whether long-term exposure to foot traffic could impact the abundance of access-indicator taxa in MDO, the abundance of these taxa was sampled at Hazard Reef and compared to the abundance of the same taxa at two adjacent sites with much lower annual densities of visitors. A stratified random sampling design was used to assess the abundance of the five access-indicator taxa found in the mid-intertidal zone at these three sites in the spring of 2009. My work demonstrated that visitor densities and patterns of use were variable among the three accessed intertidal sites in MDO. Annual visitor numbers to the rocky intertidal for the three observation sites within MDO were between 3,000-5,000 people. There was no relationship between the number of cars entering the park and the annual density of visitors to the rocky intertidal. The number of parked cars was significantly related to visitor density at one study site suggesting that under specific circumstances, controlling parking lot size may be a viable approach to managing impacts to intertidal areas. Significant differences in limpet density (60 per m2) were detected in a moderately accessed intertidal site relative to adjacent and less visited sites. The abundance of combined algae and limpets were lower at the moderate use site when the lower use sites were compared together against it. Patterns of rocky intertidal habitat use and the estimated annual visitor density suggest that some areas in San Luis Obispo County may be exposed to damaging levels of visitors. The current study identified that the abundance of one out of five experimentally identified access-indicator taxa (Rockweed, Mastocarpus papillatus, Endocladia muricata, Limpets, and Chitons) had been significantly reduced at a popular rocky intertidal site, relative to adjacent and less visited sites.

Terrestrial organic matter (TOM) constitutes an important source of energy in many aquatic environments (streams, lakes, wetlands). This is the first study to examine the role of TOM in food webs of the rocky intertidal zone. We compared the consumption of red alder leaves (Alnus rubra) to common marine sources of drifting detritus along the southern Oregon coast (Nereocystis luetkeana, Phyllospadix spp., and Fucus gardneri). We used short term (hours to days) and long term (months) feeding experiments to compare the rate of consumption among each plant species during the Spring and Fall of 2014 and 2015. In addition, we quantified the amount of TOM in beach wrack and in the drift of two streams that flowed directly to the rocky intertidal zone. We also measured the food quality of each plant species (C:N and polyphenolic concentrations). On average, the two small streams in this study transported 1,113.6 kg AFDM/m3 of TOM per day during Fall leaf abscission to the rocky intertidal zone. Also, the biomass of terrestrial leaves in beach wrack varied from negligible (2.1 g AFDM) to the dominant source of detritus (60.7 g AFDM) depending on if it was the dominant riparian plant growing along the edges of the shore. Consistent with previous research, N. luetkeana was a high quality food (C:N = 15:1; polyphenolics = 418 mg/ml), whereas F. gardneri (C:N = 22:1; polyphenolics = 8098 mg/ml) was more recalcitrant. Phyllospadix spp. was puzzling because it had low concentrations of polyphenolics (800 mg/ml) but was not consumed. Alnus rubra had a high concentration of structural compounds (C:N = 33:1) and intermediate levels of polyphenolics (3,415 mg/ml after leaching). Both short term and long term experiments showed that the rates of consumption of Spring-shed, green leaves and freshly fallen brown leaves of A. rubra were intermediate between N. luetkeana and the less palatable marine species (F. gardneri and Phyllospadix spp.). Thus, A. rubra was eaten by common intertidal consumers and may constitute an important source of energy between brief inputs of more nutritious marine resources (e.g. N. luetkeana).

This thesis describes the results of a three year study which collected larvae of the acorn barnacles Semibalanus balanoides on a rocky coastline in Fife, East Scotland. The nauplii larvae of S. balanoides are released from their parent in springtime in the United Kingdom and develop in the plankton for approximately one to two months. During this period they are transported some distance from the parent population and eventually return to the intertidal shoreline as a cyprid larval stage. The ‘decision’ to settle is a crucial point in the life history of the organism as most sessile organisms cannot move once this has occurred. The supply of larvae to intertidal shorelines was historically neglected until the 1980s. Patterns of settlement were largely considered irrelevant to distribution patterns of adults relative to postsettlement processes such as predation and competition. Despite the resurgence in “supply-side ecology” in the past 20 years there has been little development towards the measurement of larval supply. Consequently there has been very little description of fine scale or large spatio-temporal studies involving larval supply. This study demonstrates the first study directly addressing larval supply independently from larval settlement at mesoscales (metres to kilometres; days to years). Improvements were made to the passive larval trap described by Todd (2003). A conical opening was combined with the spiral trap design and a number of inlet areas were trialled (0.25cm², 0.5cm², 1cm² and 2cm²). These were tested across typical wave regimes measured with a new autonomous pressure sensing wave transducer and the 1cm² inlet was selected as the most appropriate trap design due to a balance between an increased per unit inlet larval capture and sufficient absolute larval capture so as to identify daily variation in larval supply to a site. Larval settlement has been studied extensively and is often used as a direct measure of rates of larval supply. It is widely assumed therefore that rates of settlement are a direct reflection of rates of supply, as long as settlement substrates and adult conspecific responses remain uniform. This thesis provides a means of accurately characterising the supply-settlement relationship for S. balanoides independent of substrate based responses and demonstrates that this is not the case. The relationship was found to be asymptotic, even at sites where there was low larval supply. It was concluded that density-dependent larva-larva interactions were present during the settlement of larvae and were relevant at daily temporal scales, limiting the rates of larval settlement proportional to larval density. There was no obvious effect on this relationship due to wave action however differences were observed between sites and years. Saturation of preferential environments within the tiles was observed resulting in a settlement preference cascade, with larvae being forced to settle in increasingly less preferable areas of the tiles with increasing larval density. Larva-larva interactions are demonstrated as having a considerable effect on the rates of settlement of S. balanoides.

Les activités humaines, de loisir et professionnelles, vont en s’intensifiant sur les zones rocheuses intertidales. Le piétinement associé à ces activités, le remaniement des blocs pour rechercher des espèces consommables, ne sont pas sans incidence sur les biocénoses des milieux rocheux. Les conséquences de ces activités sur la structure et la dynamique des roches du médiolittoral et des champs de blocs de bas d’estran en particulier, nécessitent d'être caractérisées. A travers l’identification des espèces et descripteurs qui répondent le plus aux perturbations "piétinement des platiers rocheux" et "retournement des blocs par les pêcheurs à pied", des indicateurs écologiques simplifiés peuvent être dégagés et faciliter, à terme, le diagnostic de l’état de conservation de ces habitats. Les processus écologiques de dégradation et de déstructuration des biocénoses sous l'effet du piétinement passent par des interactions entre espèces très complexes. Les résultats d’expérimentations in situ soulignent des phénomènes de seuils très marqués, liés en particulier à la protection jouée par les algues brunes structurantes sur les autres espèces. L'étude du retournement des blocs par les pêcheurs à pied met en évidence une phase de mortalité presque totale des organismes fixés ou peu mobiles des blocs et une faible résilience de l’habitat. Le choix de stations de référence appropriées et l’utilisation des espèces et descripteurs les plus sensibles au retournement des blocs ont permis la création de deux indicateurs de perturbation. Déclinés à deux échelles spatiales différentes, ils sont applicables en routine par les scientifiques et les gestionnaires d’aires marines protégées. / Recreational and professional activities are intensifying on the rocky intertidal. The overturning of boulders and the trampling associated with human activities, have consequences on the structure and dynamic of rocky intertidal communities. Through the identification of species and descriptors that respond more to the disturbances “trampling of mediolittoral rock platforms” and “the overturning of low eulittoral boulders by hand-fishermen”, SMART indicators (Simple, Measurable, Achievable, Realistic, and Time limited indicator) can be created for the assessment of the conservation status of these habitats. The effects of trampling were tested with control approach. Experiments in situ underlined very complex interactions between species during the ecological processes of degradation of biocenoses. High thresholds of disturbance were also observed. They were particularly related to the protection played by structuring brown algae on other species. The study of boulder’s overturning highlighted a step of almost total mortality of fixed or low mobile organisms that live on upper or lower surfaces of boulders. Results also showed a low resilience of the habitat. The use of appropriate reference situations and of the most sensitive species to the boulder’s overturning, led to the creation of two ecological indicators. Declined to two different spatial scales, they may be applied routinely by scientists and managers of marine protected areas.

Most climate change predictions focus on the response of individual species to changing local conditions and ignore species interactions, largely due to the lack of a sound theoretical foundation for how interactions are expected to change with climate and how to incorporate them into climate change models. Much of the variability in species interaction strengths may be governed by fundamental constraints on physiological rates, possibly providing a framework for including species interactions into climate change models. Metabolic rates, ingestion rates and many other physiological rates are relatively predictable from body size and body temperature due to constraints imposed by the physical and chemical laws that govern fluid dynamics and the kinetics of biochemical reaction times. My dissertation assesses the usefulness of this framework by exploring the community-level consequences of physiological constraints. In Chapter 2, I incorporated temperature and body size scaling into the biological rate parameters of a series of realistically structured trophic network models. The relative magnitude of the temperature scaling parameters affecting consumer energetic costs (metabolic rates) and energetic gains (ingestion rates) determined how consumer energetic efficiency changed with temperature. I systematically changed consumer energetic efficiency and examined the sensitivity of network stability and species persistence to various temperatures. I found that a species' probability of extinction depended primarily on the effects of organismal physiology (body size and energetic efficiency with respect to temperature) and secondarily on the effects of local food web structure (trophic level and consumer generality). This suggests that physiology is highly influential on the structure and dynamics of ecological communities. If consumer energetic efficiency declined as temperature increased, that is, species did best at lower temperatures, then the simulated networks had greater stability at lower temperatures. The opposite scenario resulted in greater stability at higher temperatures. Thus, much of the community-level response depends on what species energetic efficiencies at the organismal-level really are, which formed the research question for Chapter 3: How does consumer energetic efficiency change with temperature? Existing evidence is scarce but suggestive of decreasing consumer energetic efficiency with increasing temperature. I tested this hypothesis on seven rocky intertidal invertebrate species by measuring the relative temperature scaling of their metabolic and ingestion rates as well as consumer interaction strength under lab conditions. Energetic efficiencies of these rocky intertidal invertebrates declined and species interaction strengths tended to increase with temperature. Thus, in the rocky intertidal, the mechanistic effect of temperature would be to lower community stability at higher temperatures. Chapter 4 tests if the mechanistic effects of temperature on ingestion rates and species interaction strengths seen in the lab are apparent under field conditions. Bruce Menge and I related bio-mimetic estimates of body temperatures to estimates of per capita mussel ingestion rates and species interaction strengths by the ochre sea star Pisaster ochraceus, a keystone predator of the rocky intertidal. We found a strong, positive effect of body temperature on both per capita ingestion rates and interaction strengths. However, the effects of season and the unique way in which P. ochraceus regulates body temperatures were also apparent, leaving room for adaptation and acclimation to partially compensate for the mechanistic constraint of body temperature. Community structure of the rocky intertidal is associated with environmental forcing due to upwelling, which delivers cold, nutrient rich water to the nearshore environment. As upwelling is driven by large-scale atmospheric pressure gradients, climate change has the potential to affect a wide range of significant ecological processes through changes in water temperature. In Chapter 5, my coauthors and I identified long-term trends in the phenology of upwelling events that are consistent with climate change predictions: upwelling events are becoming stronger and longer. As expected, longer upwelling events were related to lower average water temperatures in the rocky intertidal. Furthermore, recruitment rates of barnacles and mussels were associated with the phenology of upwelling events. Thus climate change is altering the mode and the tempo of environmental forcing in nearshore ecosystems, with ramifications for community structure and function. Ongoing, long-term changes in environmental forcing in rocky intertidal ecosystems provide an opportunity to understand how temperature shapes community structure and the ramifications of climate change. My dissertation research demonstrates that the effect of temperature on organismal performance is an important force structuring ecological communities and has potential as a tractable framework for predicting the community level effects of climate change. / Graduation date: 2013 / Access restricted to the OSU Community, at author's request, from Nov. 20, 2012 - Nov. 20, 2014