**1. Introduction**

While many oceanographic studies have focused on the distribution of bioluminescence in the marine environment (Stukalin 1934, Tarasov 1956, Seliger et al. 1961, Clarke and Kelly 1965, Bityukov 1967, Lapota and Losee 1984, Swift et al. 1985, Lapota et al. 1988, Batchelder and Swift 1989, Lapota et al. 1989, Lapota and Rosenberger 1990, Neilson et al. 1995, Ondercin et al. 1995, Swift et al. 1995), little understanding of the seasonality and sources of planktonic bioluminescence in coastal waters and open ocean has emerged. Some previous studies with respect to annual cycles of bioluminescence were severely limited in duration as well as in the methods used to quantify bioluminescence (Bityukov 1967, Tett 1971). Only a few studies have measured bioluminescence on an extended basis, and these were short in duration, usually less than 2 years with long intervals between sets of measurements (Bityukov 1967, Yentsch and Laird 1968, Tett 1971). Others report data collected at different times of the year (Batchelder and Swift 1989, Batchelder et al. 1992, Buskey 1991) but do not address the seasonality of bioluminescence. Thus the detailed temporal variability of bioluminescence has never been characterized continuously over several years. Lack of such long-term studies leaves unanswered important questions regarding the role of bioluminescence in successional phenomena.

To adequately understand, model, and predict planktonic bioluminescence in any ocean, measurements must be conducted on a continual basis for at least several years in order to evaluate intra- and annual variability and long-term trends. In this study, bioluminescence was measured at two fixed stations on a daily long term basis: one in San Diego Bay (SDB) for 4 years (1992-1996) and the other for 2.5 years (1993-1996) at San Clemente Island (SCI), located 100 km off the California coast. Additional surface and at-depth bioluminescence data have been collected on a monthly and quarterly basis at both fixed stations and from a research vessel to provide a link between coastal and offshore waters. Additional factors such as seawater temperature, salinity, beam attenuation, and chlorophyll fluorescence were measured. Plankton collections were made weekly in SDB and monthly at SCI. This study provides unique correlated coastal and open ocean data collected on a long-term basis (Figure 1).

Long Term Dinoflagellate Bioluminescence, Chlorophyll,

Bight.

**3. Results** 

**3.1 Mean monthly bioluminescence** 

and Their Environmental Correlates in Southern California Coastal Waters 5

Fig. 1. Bioluminescent study area and cruise track of stations within the Southern California

Upwelling indices (North Pacific Ocean wind-driven transports) were collected from 1992 through 1996. The indices were computed for 33°N latitude (Schwing et al. 1996) and represent monthly average surface pressure data in cubic meters per second along each 100 m of coastline (Bakun 1973, Eppley 1986). Monthly rainfall data were acquired from the National Weather Service in San Diego. Nutrient and Chl *a* data were accessed from archived CALCOFI data (1992-1996) in the Bight and were averaged along CALCOFI lines 90 and 93 which run west from San Diego to the north and south of San Clemente Island (Hayward et al. 1996). Nitrates (µm L-1) and Chl *a* (µg L-1) along each of the CALCOFI transit lines (stations 93-26 to 93.45 and 90-28 to 90.53) were averaged from the surface to a depth of 50m for 12 cruises conducted from September 1992 through April 1995. These data were

used to calculate correlations with bioluminescence, rainfall, and upwelling at SDB.

data collected from 2100 h (9:00 P.M.) to 0300 h (3 A.M.) the following day.

Hourly bioluminescence data were averaged for each month. Because minimal bioluminescence was measured during daylight hours, mean monthly values were based on

Seasonal changes in bioluminescence were observed in SDB. Maximum bioluminescence (1 x 108 photons s-1 ml-1 or greater as a threshold) was measured from March through September for 1993, May through June for 1994, December through May for 1995, and March through April 1996. Minimum bioluminescence (less than 1 x 108 photons s-1 ml-1)

**2.3 Upwelling, rainfall, and seawater nutrient data bases** 
