Award: OCE-1259603

            We collected zooplankton samples at high tide to construct daily time series of abundance patterns for three consecutive winters 2014-2016 (70 day series each winter).  Preliminary evidence had suggested a number of species release eggs or embryos during large wave events.  We tested the hypothesis that these releases may lead to retention in the coastal zone under prevailing oceanic conditions associated with storms in the NE Pacific Ocean.  To test this hypothesis we identified and enumerated embryos and larvae in plankton samples (while alive), positively identify phenotypes with genetic barcoding of individual embryos or larvae by matching their sequences with those of adults in gene libraries or adult sequences we generated.  We also sampled daily recruitment to the shore (in year 2014 and part of year 2016) and carried out similar identification and enumeration to determine if spawning was correlated with recruitment in subsequent days. 

            We found that approximately 18 taxa identified to species, all with short planktonic periods (< 7 days), spawned during large wave events in winter 2014.  Species were from 4 invertebrate phyla and included a brittle star, chitons (8 species), several gastropods, bivalves, and polychaete worms.  These findings broaden beyond gastropods and barnacles known spawnings in association with storms.  The strongest factors associated with our documented spawnings were large waves, increased ocean temperature and decreased salinity (these last two are found during coastal downwelling which may retain larvae close to shore).

            Spawning intensities of all taxa, measured as the cumulative density of embryos and larvae produced by particular species over the time series, were greatly reduced by factors of 100 or more in 2015 and 2016 compared to 2014.   Very different ocean conditions from 2014 occurred in 2015 (the warm water “blob” impacted the NE Pacific coast through winter 2015) and in 2016 (an El Nino with warm waters and rough ocean conditions for most of the winter).  These conditions may have resulted in missed spawning cues, interrupted or modified reproductive cycles, and recruitment failure.  Our results show an unexpectedly large interannual variation in reproductive output that may be the result of changing ocean conditions associated with climate change.   Even if these variations are not the result of anthropogenic change, they demonstrate yet another significant (and unmeasured) source of variation in larval abundance that impacts recruitment success of marine organisms.  Reduced larval production and recruitment may negatively impact populations of invertebrates and food webs along the coastal zone of the NE Pacific. 

            We sampled plankton along offshore transects on 5 occasions after storms.  Samples were analyzed for abundance and distribution of larval phenotypes that were in our daily samples and new phenotypes.  These samples indicate that larvae may be retained nearshore on a number of instances and this might enhance local recruitment.

            We were unable to collect enough recruits with our shore traps and settlement plates to compare spawning intensity with recruitment – this was an issue of not being able to physically sample large enough areas or volumes to measure daily recruitment.

            The project resulted in production of a photographic database of phenotypes of embryos and its successful use in subsequent years by the team working on plankton sorting and identification.  We identified many dozens of stages via barcoding and can now assign species or genus names to many embryos and larval phenotypes.  The photographs and molecular identification will help in future efforts to work with coastal zooplankton in the NE Pacific.

            We trained 17 undergraduate interns (at least 3 months each) to work with zooplankton samples, sorting, identifying, and enumerating phenotypes.  Five of these interns were also involved with the photographic cataloguing and barcoding of plankton samples. Several of these undergrads also prepared and presented posters about their research at annual national or regional scientific meetings.  These research experiences were an effective way to collect data by direct examination and gave many of the interns skills to use in later research efforts.

            We trained (and graduated) 8 graduate students (3 PhD and 5 MS) with this grant support.  These students participated in daily data collection, construction of the photographic key used in type embryos and larvae from plankton samples, oversight of undergraduate interns, and cataloguing and molecular barcoding of individual embryos and larvae. Two PhD degrees and three MS degrees received major support from this research.

            To date 6 peer reviewed papers and 12 presentation (talks or posters) at national or international scientific meetings have been produced with grant support.

Last Modified: 05/22/2019
Modified by: Richard B Emlet