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A review of the kelp beds of Orange and San Diego Counties and their response to El Ninos and La Ninas from 1967 to 2001. (Abstracts).

In 1985, the San Diego Regional Water Quality Control Board (Board) stipulated in permits it issued that kelp beds near each major discharger into the Pacific Ocean be photographed annually by means of vertical and aerial infrared photography, to record as best possible the maximum areal extent of any canopies present among the 24 distinct beds that occur offshore of Orange and San Diego Counties. A consortium of dischargers was formed to develop a plan with the Board that would fulfill the prescribed requirements. Surveys were to be conducted several times per year to determine the maximum canopy extent for each year. As the surveyor selected, Dr. Wheeler J. North, had been independently assessing the kelp beds using this methodology since 1967, the historical data provided a solid foundation for the new data set.

The 34 year data set provides a synoptic view of the performance of 24 kelp beds. Although the intention was that a synoptic survey of the beds would allow a determination of the potential detrimental effects of waste. water (both heated effluent and sanitary) on the kelp beds, it also provided insight as to the effects on the kelp beds from five major El Ninos and five major La Ninas that occurred during this period. Analysis of the data indicates that the kelp beds may respond strongly to both occurrences.

This total record can be subdivided into two periods, each exhibiting very different behavior. The history from 1967 up through 1979 consisted of relatively small fluctuations. The remainder, from 1980 onward, was characterized by large fluctuations ranging from a minimum of 0.379 [km.sup.2] in 1984 to a maximum of 16.868 [km.sup.2] in 1989. The minimum value corresponded to the final year of a major El Nino while 1989 represented the first year of a large La Nina that occurred during a large stimulatory period unmatched by anything else in the 34 year history. This was followed by the largest (by some factors) El Nino of the century in 1997-1998 that resulted in the loss of 98% of the kelp canopy coverage. A large La Nina in 1999-2000 effected a recovery to about 33% of the 1989 total.

Each of the 24 kelp beds of Orange and San Diego County were monitored during these anomalous events by the means of color aerial infrared photographs taken on a quarterly basis. These photographs were taken under as close to similar conditions as possible. From these photographs, the greatest areal extent of each of the separate kelp canopies was determined for each year. Based on these data, a synopsis of the health of each of the kelp beds and the effects of these environmental perturbations, as it compares with the other kelp beds in the region, can be determined. Although it is not possible to determine the cause of a decline or decrease in a single kelp bed by aerial photographs, it is effective at showing whether the bed in question is responding to an area wide event, or if an atypical pattern has manifested. This then becomes a very cost effective tool to determine where to focus additional concentrated efforts on beds-that may be responding atypically.

M.D. Curtis (1)

W.J. North (2)

(1) MBC Applied Environmental Sciences, Costa Mesa, CA 92626 and

(2) Caltech Kerchoff Marine Laboratory, Newport Beach, CA
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Article Details
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Author:Curtis, M.D.; North, W.J.
Publication:Bulletin (Southern California Academy of Sciences)
Article Type:Brief Article
Geographic Code:1U9CA
Date:Aug 1, 2002
Words:559
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