Species of the talitrid amphipod, Megalorchestia
spp., are the dominant consumers of kelp wrack on sandy
beaches in southern California. Population dynamics of these
consumers have been studied at length by the Santa Barbara Coastal
Long Term Ecological Research program. Since multiple species can
coexist on the same beach and seemingly utilize the same
resources, we undertook a mesocosm study and pitfall trapping
survey to explore for potential temporal separation in surface
activity and how that may be mediated by tide phase.
For the mesocosm study, on a spring tide and on a neap tide, we
established 4 replicate mesocosms for each species (18.9 L buckets
filled to a depth of 20 cm with sieved dry sand and wetted using
filtered seawater) with 20 individuals in each and a fresh blade
of giant kelp (Macrocystis pyrifera) as a
food source and habitat element. Species were collected the
morning of the experiment and allowed to burrow and acclimate.
Every hour for 24 hours, the total number of individuals active on
the surface were observed for one minute and recorded.
For the pitfall trapping survey, on a spring tide and on a neap
tide, we established 4 replicate transects parallel to the high
tide strandline where twelve 470 ml cups with lids were buried
flush with the sand surface 0.5 m apart parallel to the water in
randomized order (from 1 – 12). Each group of twelve cups were
spaced 10 m apart. Seawater mixed with a few drops of dish soap
was added to the bottom of each cup to prevent trapped organisms
from escaping. One trap in each of the four groups was opened for
30 min every 2 hours for 24 hours. The organisms collected in the
traps were transferred to labeled bags and frozen for later
processing. The contents from each trap were sorted in the
laboratory, identified to species and counted.
Refer to article for detailed methods: Emery, KA, VR Kramer, NK
Schooler, KM Michaud, JR Madden, DM Hubbard, RJ Miller, JE Dugan.
2021. Habitat partitioning by mobile intertidal invertebrates of
sandy beaches shifts with the tides. Ecosphere.