Effects of predators on sea urchin density and habitat use in a southern California kelp forest

Nichols, Kathryn D.; Segui, Leah M.; Hovel, Kevin A.

doi:10.1007/s00227-015-2664-2

Cited by 22 publications

(17 citation statements)

References 54 publications

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“…This level of variability is similar to that previously documented in this system (Nichols et al. ), and is likely due to rapid, localized responses of fish predators to urchin prey in some cases. Overall, our results suggest a need to reevaluate the paradigm of top‐down control on SC rocky reefs in the absence of sea otters.…”

Section: Discussionsupporting

confidence: 88%

“…However, sheephead and other predators only regulated purple urchins when large red urchins were absent, a condition consistent with fished areas but not typically observed within MPAs (Nichols et al. , Teck et al. ).…”

Section: Discussionsupporting

confidence: 54%

“…Red urchins are also targeted in a fishery and are most abundant in marine reserves (Nichols et al. , Teck et al. ), so their ability to mediate interactions between purple urchins and rocky reef predators may be spatially variable.…”

Section: Introductionmentioning

confidence: 99%

“…Large red urchins can provide refuge to smaller urchins through a spine canopy refuge (Tegner and Dayton 1977) but are also an alternative prey item for both sheephead and spiny lobsters. Red urchins are also targeted in a fishery and are most abundant in marine reserves (Nichols et al 2015, Teck et al 2017, so their ability to mediate interactions between purple urchins and rocky reef predators may be spatially variable. We discriminated between potential mechanisms underlying the observed mortality patterns by characterizing the functional responses of spiny lobsters and quantifying the aggregative response of fishes foraging on urchins in the field.…”

Section: Introductionmentioning

confidence: 99%

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Experiments reveal limited top‐down control of key herbivores in southern California kelp forests

Dunn

Hovel

2019

Ecology

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Predator responses to gradients in prey density have important implications for population regulation and are a potential structuring force for subtidal marine communities, particularly on rocky reefs where herbivorous sea urchins can drive community state shifts. On rocky reefs in southern California where predatory sea otters have been extirpated, top‐down control of sea urchins by alternative predators has been hypothesized but rarely tested experimentally. In laboratory feeding assays, predatory spiny lobsters (Panulirus interruptus) demonstrated a saturating functional response to urchin prey, whereby urchin proportional mortality was inversely density‐dependent. In field experiments on rocky reefs near San Diego, California, predators (primarily the labrid fish California sheephead, Semicossyphus pulcher) inflicted highly variable mortality on purple urchin (Strongylocentrotus purpuratus) prey across all density levels. However, at low to moderate densities commonly observed within kelp forests, purple urchin mortality increased to a peak at a density of ~11 urchins/m2. Above that level, at densities typical of urchin barrens, purple urchin mortality was density‐independent. When larger red urchins (Mesocentrotus franciscanus) were offered to predators simultaneously with purple urchins, mortality was density‐independent. Underwater videography revealed a positive relationship between purple urchin density and both the number and richness of fish predators, but these correlations were not observed when red urchins were present. Our results demonstrate highly variable mortality rates across prey densities in this system and suggest that top‐down control of urchins can occur only under limited circumstances. Our findings provide insight into the dynamics of alternate community states observed on rocky reefs.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experiments reveal limited top‐down control of key herbivores in southern California kelp forests

Dunn

Hovel

2019

Ecology

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“…In affected areas, urchins may persist for years after consuming the canopy algae, just by living on biofilms, drifting macroalgae and algal recruits, while maintaining the barren ground (Leinaas and Christie 1996). Without exaggeration, the macroalgal/urchin system constitutes a central corner-stone for the conceptual development of community ecology (e.g., Paine and Vadas 1969;Mann 1977;Paine 1980;Estes et al 1998) and various aspects of the topic are frequently reported in this journal (some recent papers include, e.g., Fagerli et al 2015;Nichols et al 2015). However, to this very day, there are still apparent gaps in our knowledge regarding many of the processes and mechanisms involved in defining the two alternative stable states of these ecosystems (Filbee-Dexter and Scheibling 2014; Ling et al 2015).…”

Section: Nos Numerus Sumus Et Fruges Consumere Natimentioning

confidence: 99%

Macroalgal grazing by the green sea urchin: born to consume resources

Kraufvelin

2017

Mar Biol

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information of consumption rates and factors controlling the feeding of a common and widely distributed sea urchin species at higher latitudes in the northern hemisphere, the green sea urchin, Suskiewicz and Johnson (2017) deliver a vital synthesis for improved understanding of this specific phenomenon, its dynamics and mechanisms, as well as its ecological consequences.The main results from the literature review by Suskiewicz and Johnson (2017) concern factors that under laboratory conditions have been reported to control sea urchin consumption rates such as urchin size, urchin reproductive state, water temperature and algal species (food type). Although bigger urchin individuals as expected ate more than smaller individuals, the small ones consumed food at the same rates as the big ones, suggesting that simple estimations of total urchin biomass may be sufficient for the evaluation of the potential herbivore pressure in an area. A more surprising finding was that temperature did not have any clear impact on feeding rates presenting quite ambiguous results when viewed in the larger picture. The consumption of different types of macroalgae and of the same algal species during different occasions and in different regions was also puzzling at times. All algal taxa offered to the urchins were eaten and even though some species clearly were preferred above others, the actual favoured ones often differed among regions and typically ignored species could at certain places be eaten at high rates.Among the central take home messages from this review, the estimates of the maximum amounts of algae that an urchin can consume stand out explicitly as these values are quantifying key elements of the macroalgal/urchin dynamics. If consumption rates together with changes in urchin abundance are coupled with macroalgal productivity estimates of a location, ecological tipping points in the transition from macroalgal forests to barren grounds may

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Spiny lobster predation of barrens‐forming sea urchins is not limited by body size, but may be overstated

Day,

Knott,

Swadling

et al. 2024

Ecosphere

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Worldwide, lobsters are considered key predators that control urchin populations. It has been widely reported that lobster size plays a significant role in the size of urchins they feed on, as does the size of the urchin. Generally, it is thought that small palinurid “spiny” lobsters measuring less than 120 mm carapace length (CL) are morphologically incapable of eating urchins, while large lobsters are voracious predators. Urchin size is expected to affect predation with larger urchins of greater than 90 mm test diameter (TD) presenting the most difficult prey. These generalities, however, have not been quantitatively tested for the eastern spiny lobster Sagmariasus verreauxi and recently the accepted size paradigm for lobsters eating urchins has come into question. The aim of this study was to assess whether lobster predation on urchins would differ with urchin size or species, or the size of lobster. Our results indicate that S. verreauxi does not fit the common lobster patterns regarding urchin predation. There were generally low rates of predation and a significant negative relationship between feeding and both lobster size and urchin size. We found that small lobsters were capable urchin predators with a higher likelihood of eating urchins than larger lobsters, which were more reluctant predators. While we did find the expected effect of smaller urchins being significantly more vulnerable prey, there was none of the expected size limitations for small lobsters eating large urchins and predation did not differ between urchin species, indicating that this was a general pattern. Overall, we observed low rates of predation, suggesting that either S. verreauxi may not be a key urchin predator like other lobster species elsewhere, or that small lobsters are underestimated as urchin predators in temperate marine ecosystems.

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Effects of predators on sea urchin density and habitat use in a southern California kelp forest

Cited by 22 publications

References 54 publications

Experiments reveal limited top‐down control of key herbivores in southern California kelp forests

Experiments reveal limited top‐down control of key herbivores in southern California kelp forests

Macroalgal grazing by the green sea urchin: born to consume resources

Spiny lobster predation of barrens‐forming sea urchins is not limited by body size, but may be overstated

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