Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO): intertidal component
- Pete Raimondi
University of California, Santa Cruz
- Mark Carr
University of California, Santa Cruz
One of the greatest challenges for conservation biologists is to unravel the causes of variation in biological communities. All conservation efforts in the nearshore environment, such as the design of marine reserves, are crucially dependent on understanding these dynamics. Determining the causes of community variation is a particularly daunting task for nearshore marine communities because three prominent, interdependent sources of variation are poorly understood: coastal nutrients and productivity (so-called "bottom-up" effects), dispersal, and oceanic climate. The goal of PISCO is to increase understanding of these issues, individually and collectively.
The core of PISCO research is a sampling program that combines studies of variability in ocean climate with simultaneous multi-species experimental studies of larval and adult populations over most of the U.S. West Coast. We focus on tractable ecosystems - shallow water, hard substratum nearshore communities - that have proven to be model communities for both experimental and theoretical studies. By coordinating simultaneous studies over a range of spatial scales from the individual organism to the regional coastline, this study will provide the first examination of the causes and consequences of variation in marine populations on spatial scales that are relevant to marine populations and conservation.
Rocky intertidal habitats support diverse communities of algae, invertebrates, and fish. In 1999, PISCO began a large-scale, long-term study of the patterns of species diversity in these habitats and the physical and ecological processes responsible for structuring these communities. The intertidal component of the PISCO project aims to understand patterns in biodiversity and temporal variation in community structure and the mechanisms that are responsible for both, over a broad temporal and spatial scale. Within the Monterey Bay National Marine Sanctuary (MBNMS), PISCO has developed three main approaches to explore these intertidal processes: Core monitoring, Community Structure surveys, and Biodiversity surveys (Figure 1). The development of these standardized survey designs and sampling protocols is central to the success and value of the expansive scale of this monitoring program.
At 6 sites within the MBNMS, PISCO Core monitoring is conducted on a monthly basis, to measure the following:
Larval recruitment (barnacles and mussels) (Figures 2, 3, 4)
Fecundity rates (barnacles and mussels) (Figure 4)
Sea surface temperature (Figure 4)
Water nutrient and chlorophyll levels
Growth rates (mussels)
The PISCO Core protocols are carried out at multiple sites along the west coast by UC Santa Cruz, UC Santa Barbara, and Oregon State University. For more information, please visit www.piscoweb.org.
At 19 sites within the MBNMS, Community Structure surveys are conducted 3 times per year (fall, spring, and summer [recruitment only]). Data is collected on the following:
Sea surface temperature
Photo quadrats (Anthopleura, Balanus, Chthamalus, Endocladia, Fucus, Hesperophycus, Mastocarpus, Mazzaella, Mytilus, Pelvetiopsis, Pollicipes, Silvetia)
Counts and size frequency (abalone, seastars, and owl limpets) (Figure 5)
Transects (surfgrass, Postelsia)
Mobile invertebrate quadrat counts
The Community Structure surveys were modeled after an existing monitoring program funded by the Minerals Management Service (MMS) in 1992. This same community structure protocol has since been adopted by MARINe (Multi-Agency Rocky Intertidal Network), which is a partnership of local, State, and Federal agencies, universities and private organizations. Currently, MARINe conducts these surveys at 89 sites ranging from the Oregon-Washington border down to the California-Mexico border. For more information, please visit www.marine.gov.
At 15 sites within the MBNMS, Biodiversity surveys are conducted every 3-5 years (Figure 6). Information collected includes the following:
Point contact identification
Mobile invertebrate quadrat counts
Seastar band counts
Tidal height topographic measurements (Figures 7, 8)
The Biodiversity surveys are part of a long term monitoring project with sites ranging from Southeast Alaska down to Baja California Sur, Mexico. For more information, please visit http://cbsurveys.ucsc.edu.
Summary to DatePISCO Core recruitment monitoring helps to quantify larval input into the intertidal environment. Long-term quantification of recruitment allows us to distinguish long-term trends from natural annual and seasonal variability.
The Community Structure monitoring approach is based largely on surveys that quantify the percent cover and distribution of algae and invertebrates that constitute these communities. This approach allows us to quantify both the patterns of abundance of targeted species as well as characterize changes in the communities they reside in. Such information provides managers with insight into the causes and consequences of changes in species abundance. Such changes in species and their habitats result from human or non-human factors and as such form the basis of "ecosystem-based management" of rocky intertidal communities.
The Biodiversity survey findings reveal distinct groups, where the composition of the intertidal communities is similar. The sites within MBNMS are in a group that extends from Point Reyes, California to Point Conception, California. This area is characterized by a combination of northern and southern invertebrate and algal species. High larval recruitment in this region also affects the composition of intertidal communities.
This project is on going. We continue to collect data regularly at all of our sites. In addition, we continue to increase the number of sites we sample each year. As part of the Marine Life Protection Act (MLPA) Initiative, we will be adding 11 new Community Structure and Biodiversity sites in 2007-2008.
The findings presented below are unpublished, preliminary results, and should not be cited, copied, or referenced without the permission of the principal investigators.
- Annual recruitment totals for Chthamalus (a barnacle) show a marked difference in Northern and Southern sites. There is an overall trend of increased recruitment over time, which coincides with increased sea surface temperature levels, indicating a link between oceanography and recruitment. When comparing the proportion of Chthamalus that are brooding each month across all years at five sites within the MBNMS, a similar trend is seen, with the highest proportion of brooding adults present in March. A high proportion of recruitment happens twice during the year; once right after reproduction in the Spring, and once again in the Fall (Figure 4).
- Populations of juvenile and adult Pisaster ochraceus (a sea star) and Lottia gigantea (an intertidal limpet) regularly fluctuate over time (Figure 5).
- Site topography shows a strong influence on the biology at each site (Figure 7).
- Dispersal & Recruitment
- Size structure
- Chl A
- Substrate characterization
Study MethodsPISCO Core methods:
For each intertidal site there are 5 replicates on each of 2 different artificial substrates (tuffies and plates) targeting barnacle and mussel recruitment. There are also 5 replicates of rock clearings for barnacle recruitment. These substrates are gathered and re-deployed on a monthly basis, and the clearings are counted and re-cleared. Temperature loggers are zip-tied into small metal cages that are secured to the rock, and temperature is collected at a rate of every 15 minutes. There is one logger per site, and data are recovered once every 2 months. Water is collected once a month from a 1 meter depth, using acid washed opaque bottles on the end of a 3 meter stick. Sample processing is done within 1 hour. For mussel growth, 50 mussels are placed in 5 replicates per site.
Community Structure methods:
Barnacle recruitment is monitored using permanent 10x10 cm clearings and recruitment plates that are replaced every 4 months. Permanent photoplots are established in a variety of assemblages. Cover of the major taxa is determined by point-contact photographic analysis for all plots except barnacles, which are scored in the field to allow samplers to distinguish Chthamalus spp. from Balanus glandula. Counts of mobile invertebrates occurring within the photo quadrats are also done in the field. Additional permanent plots are established for large motile species such as owl limpets, black abalone and seastars. Permanent line transects are used to estimate the cover of surfgrass while band transects are used to count Postelsia. Photographic overviews and field notes are used to describe general conditions at the site and to document the distribution and abundance of organisms not found within the photoplots.
The Biodiversity surveys are done at each site on a less frequent basis (approximately every 3-5 years). They incorporate a permanent 30 m baseline transect that runs parallel to shore above the organisms in the high zone. Eleven transects are laid out towards the ocean from this baseline transect at each 3 m mark, starting at 0 m. Transects are then sampled using a point contact method in which the organism or substrate occurring directly under each point is recorded as well as the two closest species. Point spacing varies according to transect length. Mobile invertebrates are counted in randomly placed 1/4 m2 quadrats along each transect (3 per line/33 per site), since the point contact method does not adequately capture the mobile species. Sea stars and abalone are also counted in a 2 m swath centered over each transect, and their location (along transect) to the nearest 0.5 m is recorded. Finally, topographical maps are made of the site using a laser leveler and a laser sensor attached to a stadia rod. For the full sampling protocols for the Biodiversity surveys, please visit: http://cbsurveys.ucsc.edu/sampling/datasheets.html
Figures and Images
Figure 1. Map of intertidal sites surveyed by PISCO within the MBNMS, and the type(s) of monitoring conducted at each site.
Figure 2. Installation of the larval recruitment plates and tuffies used at PISCO Core Monitoring sites. Many intertidal species reproduce by spawning into the water column, and the larvae that form can be moved by ocean currents for hours, days or weeks before they settle onto the shoreline. These plates and tuffies capture some of those settling larvae.
Figure 3. Overall number of barnacle recruits (Chthamalus and Balanus) from 2000-06, and mussel recruits (Mytilus californianus) from 2000-04, at five sites within the MBNMS.
Figure 4. Annual recruitment totals for the intertidal barnacle Chthamalus, 2000-06 (upper left); sea surface temperature deviation at PISCO Core sites, 2000-05 (lower left); proportion of population of Chthamalus with broods, by month (upper right); timing of recruitment of Chthamalus, by month (lower right).
Figure 5. Size frequency of juvenile and adult Pisaster ochraceus (ochre stars) and the giant owl limpet Lottia gigantea at four sites with in the MBNMS, from 2000-07.
Figure 6. Sampling grid used for Biodiversity surveys at Andrew Molera State Park in Big Sur.
Figure 7. Topographical map of a Biodiversity site, with vertical distribution of 4 species and the location of tide pools overlaid. In order to sample a 30 m baseline, the site was split into 2 sections.
Figure 8. Measuring tidal heights at Fitzgerald Marine Reserve, using a laser sensor attached to a stadia rod.