We sampled sea urchins from both urchin barrens and kelp forests at
two reefs, Naples Reef (34° 25’ N, 119° 57’ W) and Arroyo Quemado
(34° 28’ N, 120° 07′ W), from the kelp forest at Mohawk Reef (34°
23’ N, 119° 43’ W), where there was no significant barren area, and
from Jackpot Seep (34° 24’ N, 119° 52’ W), a rocky reef with active
hydrocarbon seeps, at depths of 10-14 meters from February to April
2016. Urchin barrens were characterized by a lack of giant kelp,
sparse macroalgae in general, and high densities of sea urchins.
Jackpot Seep is a rocky reef with active hydrocarbon seeps and
little algae, where we observed urchins grazing on microbial mats
that characterize seeps in the region.
Twelve adult sea urchins of each species were collected in each of
the three habitats, totaling 36 per species. To characterize the
microbial communities of potential food items for the urchins, we
also collected six samples of giant kelp (Macrocystic
pyrifera) blades, three from Mohawk Reef and three from
Arroyo Quemado, and 15 samples of bacterial mats from Jackpot Seep.
DNA from urchin gut, kelp, and microbial mat samples was extracted
and The V3-V4 region of the 16S ribosomal gene was amplified.
For detail method, please see the method section in article: Miller
PM, Lamy T, Page HM, Miller RJ. Sea urchin microbiomes vary with
habitat and resource availability. Accepted in Limnology and
Oceanography Letters.