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Free-spawning marine animals such as the red abalone,Haliotis rufescens,need densely aggregated populations for successful external fertilization in the water column. Red abalones are known to contract their muscular bodies while spawning, which may increase gamete dispersal by pushing plumes of gametes higher up into the water column, ushering gametes within reach of other spawning adults. We hypothesized that the heights of egg plumes would increase with increasing contractile forces. We measured the contractile forces of 15 female adult red abalones and captured the changes in the heights of the resultant egg plumes during free-spawning using high-speed videos at the Cabrillo Marine Aquarium, San Pedro, California between September 2019 and February 2020. We found that the egg plume heights were positively and non-linearly impacted by the contraction forces, and abalones possessing a third open respiratory pore had plumes that were 2.69 cm taller on average. We also found that larger gonad widths positively impacted the plume heights. This new information about the impact of abalone contraction forces on egg plumes will enhance our knowledge of abalone reproductive behaviors, launch future studies, and guide restoration strategies and policies for protected abalone species.

This study examines the bryozoan fauna encrusting on the common Pacific half-slippersnail,Crepipatella lingulata. This suspension-feeding calyptraeid gastropod is common at shallow depths off the coast of California and is also common in the fossil record. The shell lengths ofC. lingulataspecimens dating back to the late Pliocene-early Pleistocene were examined, as well as the area of shells encrusted with bryozoans. Holocene shells were significantly larger than other shells, and modern (specimens collected in the present day) encrusted shells were significantly shorter than encrusted shells from the ancient past, but the latter could reflect collection bias. I also determined that modern shells are more fully covered with bryozoans than fossil shells. However, there was significant statistical interaction in the Holocene and modern data; thus, if more specimens were to be added that were relatively less prone to sampling biases from these time periods, the observed patterns could change. Finally, I identified bryozoan species encrusting on modernC. lingulatashells: 34 of the 41 specimens examined were found to be the speciesRhynchozoon rostratumand, because one bryozoan species seems to dominate the encrustation, this implies a symbiotic association betweenC. lingulataandR. rostratum.

Estuaries have been armored with artificial habitat to protect coastal infrastructure from erosion, but armoring may have negative ecological impacts. Other shoreline protection strategies, such as eco-engineered seawalls and living shorelines, offer more natural, rugose substrata to native species while limiting coastal erosion. The Port of San Diego plans to build a living shoreline using concrete reef balls that recruit the native oyster,Ostrea lurida, but the Port wants to avoid recruitment of non-indigenous species (NIS), especially the non-indigenous oyster,Crassostrea gigas. I modified concrete tiles that acted as proxies for reef balls with added shell cover and rugosity to determine if there is a treatment that can achieve these goals. I deployed six treatment types embedded into 15 x 15 cm concrete tiles: two with surface shell (100% cover of crushed or large shell fragments), two without shell (smooth or rough concrete), and two reference treatments (50% shell cover and terracotta). Seven replicates per treatment were deployed at two sites in San Diego Bay and one site in Newport Bay, California, USA, at 0 and 0.6 m Mean Lower Low Water (MLLW) from May to September 2018. I used three-way ANOVAs, ANCOVAs, and PERMANOVAs to test for the effects of tile orientation, tidal elevation, shell cover, and rugosity on the recruitment of oysters and other fauna.O. luridarecruited in higher abundance and generally higher percent cover thanC. gigasonto all treatments across all sites at 0 m MLLW and treatments that combined 100% shell cover with high rugosity at two of three sites at 0.6 m MLLW, a tidal elevation to whichO. luridararely recruits. Some NIS recruited in lower abundance to 100% shell treatments and/or rugose treatments, although the effects were not consistent across species. Recruitment strength of both native and NIS varied across sites and treatments and should be tested on a site-specific basis prior to reef ball deployment, but I suggest projects that utilize reef balls in living shoreline designs in southern California should generally add shell cover and rugosity to the concrete to favor native species and discourage NIS.

Mytilus californianus, the California mussel, is a foundation species and dominant space-holderin the rocky intertidal zone, an environment that goes through extreme temperature shifts on a daily basis as organisms are submerged in seawater during high tide and exposed to terrestrial conditions during low tide. Mussels create protein ‘anchors’ called byssal threads that allow them to attach to rocks and each other.To my knowledge, no studies have addressed the role of temperature during low tide on attachment strength of mussels, despite the clear importance of this topic in the context of the rising temperatures predicted with a changing climate.Iused laboratory manipulations to investigate how temperature during low tide and the number of low-tide exposures affected three components of mussel attachment: byssal thread production, individual mussel attachment strength, and single byssal thread thickness (as a proxy for strength). We collected mussels from sites in Washington and California and set up a five-day lab experiment with two types of treatments: number of low tide exposures (exposure on the first day followed by four days of submersion or exposure each day for five days) and temperature during low tide exposure (ambient or elevated temperature).Overall, neither number of low tides nor low tide temperature affected the number of byssal threads produced by mussels, but the number of low tides had strong effects on the amount of force required to remove mussels from the substratum and on the thickness of individual byssal threads (a proxy for thread strength). Mussels exposed to multiple low tides required less force to remove from the substratum and had thinner (and thus weaker) threads than mussels exposed to a single low tide, and the combination of multiple low tides and warm low tide temperatures had negative impacts on mussel attachment. In the context of a changing climate, these data help us to understand important hurdles to persistence for this ecosystem engineer.

Organisms in the intertidal zone, which experience terrestrial conditions during low tide emersion and are submerged in seawater during high tide, are threatened by sea level rise (SLR) which could reduce annual emersion time by over 50% over the next 100 years. I tested the hypothesis that coastal squeeze and SLR conditions would negatively impact the performance of individuals of the canopy-forming seaweedPelvetiopsis californica.Over four seasons, I performed population surveys at four sites in southern California, to collect baseline data on differences in physiology, reproduction, and tissue chemistry between individuals at the high and low edges of the natural vertical distribution for this species. At two of these sites, I conducted a 16-month manipulative experiment with three treatments: marked in place individuals (transplant controls: MIP) were not moved; transplant individuals within the natural vertical distribution (In Place Transplants=IPT) were relocated at the same tidal elevation; and Sea Level Rise Transplants (SLRT) were moved to a lower tidal elevation, exposing them to shorter emersion times (= SLR conditions). I assessed algal performance through monthly measurements of size, cover of epiphytic seaweeds (which grow on the host, blocking light and nutrients), reproductive potential, and photosynthetic potential (as Maximum Quantum Yield). While SLRT individuals had high photosynthetic potential and did reproduce, they lost more tissue (on average, 25% of their original length) than individuals in other treatments. More than three times as many individuals in the SLRT treatment were infected with epiphytic seaweeds than in IPT or MIP treatments. These data indicate substantial risk of SLR to populations of this seaweed and may help managers develop mitigation efforts for this important intertidal producer.