Click
here to close Hello! We notice that
you are using Internet Explorer, which is not supported by Echinobase
and may cause the site to display incorrectly. We suggest using a
current version of Chrome,
FireFox,
or Safari.
Artificial light at night and warming impact grazing rates and gonad index of the sea urchin Centrostephanus rodgersii.
Caley A
,
Marzinelli EM
,
Byrne M
,
Mayer-Pinto M
.
???displayArticle.abstract???
Artificial light at night (ALAN) is a growing threat to coastal habitats, and is likely to exacerbate the impacts of other stressors. Kelp forests are dominant habitats on temperate reefs but are declining due to ocean warming and overgrazing. We tested the independent and interactive effects of ALAN (dark versus ALAN) and warming (ambient versus warm) on grazing rates and gonad index of the sea urchin Centrostephanus rodgersii. Within these treatments, urchins were fed either 'fresh' kelp or 'treated' kelp. Treated kelp (Ecklonia radiata) was exposed to the same light and temperature combinations as urchins. We assessed photosynthetic yield, carbon and nitrogen content and C : N ratio of treated kelp to help identify potential drivers behind any effects on urchins. Grazing increased with warming and ALAN for urchins fed fresh kelp, and increased with warming for urchins fed treated kelp. Gonad index was higher in ALAN/ambient and dark/warm treatments compared to dark/ambient treatments for urchins fed fresh kelp. Kelp carbon content was higher in ALAN/ambient treatments than ALAN/warm treatments at one time point. This indicates ocean warming and ALAN may increase urchin grazing pressure on rocky reefs, an important finding for management strategies.
Figure 3. . Effect of light (ALAN or dark night) and warming (ambient or warm) on mean quantum yield (FV/FM) (±s.e.) of treated E. radiata by week. Kelp was collected in weeks 1, 5 and 7, and the graph is faceted by this collection group (collection 1, 2 and 3, respectively). Error bars represent ± s.e.
Figure 1. . Effect of light (ALAN or dark night), warming (ambient or warm) and kelp treatment (fresh or treated) on mean daily grazing of kelp (±s.e.) by C. rodgersii standardized by urchin wet weight. Measurements were repeated on two sample nights for each tank per week. Graph (a) shows values by week. In graph (b), means and s.e. are averaged across weeks for fresh kelp, as there were no interactive effects of weeks or any week effects on grazing rates for urchins fed fresh kelp. Left graph in (b) shows treatment with urchins fed fresh kelp (n = 10), right graph in (b) shows treatments with urchins fed treated kelp (n = 4) (i.e. urchins were fed kelp exposed to the same light and heat treatments). Error bars represent ± s.e.
Figure 2. . Effect of light (ALAN or dark) and temperature (ambient or warm) on mean gonad index (±s.e.) of urchins fed fresh kelp (a) or treated kelp (b). Gonad index is gonad wet weight as a proportion of total wet weight (%). Panel (a) shows treatments with urchins fed fresh kelp (n = 10), (b) shows treatments with urchins fed treated kelp (n = 4) (i.e. urchins were fed kelp exposed to the same light and heat treatments). Error bars represent ± s.e.
Figure 4. . Effect of light (ALAN or dark) and warming (ambient or warm) on mean (±s.e.) (a) log-transformed C : N ratio, (b) C content and (c) N content of treated kelp by week and treatment. Juvenile kelp was collected in weeks 1, 5 and 7, and the graph is faceted by this collection group (collection 1, 2 and 3, respectively). Error bars represent ± s.e.
