History of kelp beds (Macrocystis) in Orange and San Diego Counties, California

North, Wheeler J.; James, David E.; Jones, L. G.

doi:10.1007/bf00049029

Cited by 21 publications

(15 citation statements)

References 6 publications

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“…Nitrate and regional kelp canopy cover-The relationship between giant kelp and the nutrient (nitrate) climate on the inner shelf was examined using an aerial photographic record of 14 kelp forests (Table 2) off San Diego and Orange Counties. Kelp-forest canopy cover in southern California, from the Mexican border to the southern border of Los Angeles County, has been estimated annually from aerial photographs since 1967 (North et al 1993). Aerial surveys have been conducted two to four times each year over that period, and the annual maximum coverage observed for each kelp forest was used as the annual estimate of canopy cover.…”

Section: Measuredmentioning

confidence: 99%

“…''resource '' or ''bottom-up''), cool high-nutrient periods such as La Niñ as are typically associated with increased levels of giant kelp productivity, growth, survival, and reproduction (Dayton et al 1999). Yet despite the well-established relationship between temperature and nitrate (Zimmerman and Kremer 1984), temperature accounts for less than half of the variability in proxies of giant kelp abundance such as canopy area, density, or harvest within the CCS (North et al 1993;Tegner et al 1996). Despite this, macroalgal stands at kelp-forest scales and greater are generally considered climate (cf.…”

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confidence: 99%

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The response of giant kelp (Macrocystis pyrifera) in southern California to low‐frequency climate forcing

Parnell

Miller²,

Cody

et al. 2010

Limnology & Oceanography

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The nutrient climate on the inner shelf off southern California changed markedly across the 1976-1977 North Pacific climate regime shift. With respect to giant kelp (Macrocystis pyrifera) canopies off southern California, the nitrate climate shifted from relatively replete conditions prior to the regime shift to depleted conditions afterward, and the dynamics of 14 giant kelp forests appeared to change as a result. The response of giant kelp to nutrientreplete years before the regime shift was dampened compared to their response afterward. The sensitivity of these kelp-forest canopies to nutrient limitation appears to have increased since the regime shift. This intensification of physical control after 1977 is evident in the strong correlation of seawater density (s t ) and M. pyrifera density. The linear fit of the percent of time the 25.1 s t isopycnal bathes the inner shelf, accounted for , 71% of the variability in kelp density off Point Loma, and the median depth of this isopycnal has deepened , 5 m since the regime shift. The wave climate also intensified beginning in the early 1970s. The dampened kelp response prior to the regime shift was likely due to greater biological control of kelp canopies via consumer and competitive processes (i.e., biological modulation) or decreased physical control at possibly many trophic levels. Our results suggest that the response of kelp forests to El Niñ o Southern Oscillation events is mediated by lower frequency climate modes that may modulate the regulatory importance of biological and physical processes on giant kelp.

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Section: Measuredmentioning

confidence: 99%

mentioning

confidence: 99%

The response of giant kelp (Macrocystis pyrifera) in southern California to low‐frequency climate forcing

Parnell

Miller²,

Cody

et al. 2010

Limnology & Oceanography

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“…Over the last century, the Point Loma kelp canopy has undergone frequent fluctuations, ranging from being essentially absent at least three times to covering almost 10 km 2 (North et al 1993, Tegner et al 1996a. We have also documented such temporal fluctuations in population densities of Macrocystis and the understory kelps Pterygophora californica and Laminaria farlowii ( Fig.…”

Section: Long-term Patterns Of Density and Distributionmentioning

confidence: 99%

Sliding Baselines, Ghosts, and Reduced Expectations in Kelp Forest Communities

Dayton¹,

Tegner²,

Edwards³

et al. 1998

Ecological Applications

161

235

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The detection of trends in ecosystems depends upon (1) a good description of the foundation or benchmark against which changes are measured and (2) a distinction between natural and anthropogenic changes. Patterns and mechanisms observed over 25 years in a large kelp forest suggest that definition of a meaningful benchmark is impossible, because many of the large animals have been gone for years to decades, and kelps are sensitive to large-scale, low-frequency El Niñ o-Southern Oscillation events and longer term regime shifts. A shift in the oceanographic climate has significantly reduced the average size and carrying capacity of the dominant plant. The animals that have been functionally removed from the community include sea otters, black sea bass, yellowtail, white sea bass, and abalones. Other species are still present, but fisheries have had huge effects on the abundances, size-frequencies, and/or spatial distributions of sheephead, kelp bass, rays, flatfish, rock fish, spiny lobsters, and red sea urchins. Now even sea cucumbers, crabs, and small snails are subject to unregulated fishing. The plants continue to exist without a hint of the effects of the loss of so much animal biomass. Furthermore, most of the megafauna have been removed with very little documentation or historical understanding of what the natural community was like. Thus, our ability to separate anthropogenic impacts from the ''natural'' dynamics of the system is severely compromised. We discuss the importance of both an ecosystem focus on productivity and careful monitoring of as many populations as possible. In addition, we show that this community is not tightly integrated with mutual dependencies; hence, many species can be removed without much affecting the rest of the ecosystem.

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“…This and associated aerial time series have been used for both ecological research and resource management purposes. North, James, and Jones (1993) used a 25-year time series to study how maximum annual canopy extent was affected by climate oscillations, storms, and human impacts, such as waste-water discharge. The spatial variability of the effect of wave disturbance on kelp, and the spatial and temporal dynamics of canopy coverage around the Monterey Peninsula were assessed using aerial photographs (Donnellan, 2004;Graham et al, 1997).…”

Section: Introductionmentioning

confidence: 99%