Eelgrass (Zostera marina) meadows provide important habitat to waterfowl, invertebrates, and fishes and are the focus of restoration efforts in Washington State. Given the variation in water temperatures of different Pacific Northwest eelgrass habitats, we investigated how water temperature of source locations could affect how the eelgrass could perform as potential donor candidates. In our study, the sites designated for eelgrass shoot donation differed in water temperature; Padilla Bay was generally warmer than Ship Harbor. We hypothesized that plants from the warm site would perform better in warmer temperatures and handle warm temperature extremes. We conducted a mesocosm experiment in which we manipulated temperature and measured eelgrass growth, morphology, and decay. Eelgrass in the warmed treatment decreased in length compared to plants reared at the ambient seawater temperature (control), with Ship Harbor eelgrass decreasing in shoot length more than Padilla Bay eelgrass. The eelgrass from Ship Harbor started to decrease in length at 21 days, compared to 28 days for Padilla Bay. Furthermore, the warmed treatment had more decay after 28 days than the control treatment and eelgrass from Ship Harbor decayed more severely than those from Padilla Bay. Surprisingly, new growth from Ship Harbor was greater than that from Padilla Bay. Our results suggest that Padilla Bay eelgrass could have been better acclimated to warmer temperatures, but the increased temperature still lead to a decrease in performance. The implication for eelgrass restoration is that the temperatures of donor and receiving sites should be similar to improve eelgrass transplant success.

Organic matter, such as detritus, occurs naturally in marine sediments. However, anthropogenic activities, such as historical timber industry practices and nutrient enrichment (eutrophication) leading to algal blooms, have enriched organic matter in marine sediments, compromising the stability of benthic communities. Added organic material can facilitate microorganisms, which alter the chemistry of the water in marine sediment. This study focused on factors associated with the success of benthic anaerobic bacteria that reduce sulfate into sulfide, which can be detrimental to organisms living in and on the sediment. We investigated if wood or algae would be a more productive carbon source for sulfate reducing bacteria and if grain size, fine versus coarse, would affect the amount of sulfide produced by anaerobic bacteria. Sediment microbial communities were cultivated in a four-week long mesocosm experiment in which wood or algae carbon sources were mixed in fine or coarse sediment. We measured sulfide levels throughout the experiment to determine which treatments were most productive. We found that algae led to earlier and higher sulfide levels within four weeks, as compared to wood. Furthermore, fine grained sediment produced higher concentrations of sulfide, particularly in the presence of algae. Our findings suggest organic material in the form of algae, such as from algal blooms, is a more readily available source of carbon for sulfate reducing bacteria. Future research could extend the timeline of an experiment to investigate what sulfide levels may be produced with wood in sediment.

Eelgrass beds in the Salish Sea provide habitat for various organisms, including algal epiphytes and invertebrate grazers. The relationships amongst eelgrass, epiphytes, and grazers are highly complex. Epiphytes have been shown to have a negative effect on eelgrass growth, and epiphyte removal by grazers has been shown to have a positive effect on eelgrass fitness. In some experiments, epiphyte and grazer presence has been shown to have a neutral effect on eelgrass. Therefore, in this study we examined the interactions between Zostera marina L, epiphytes, and a native marine invertebrate gastropod Haminoea vesicula to measure how these relationships impacted eelgrass growth as a proxy for performance. We collected specimens from two different locations with contrasting gastropod and epiphyte presence- Padilla Bay and Ship Harbor, Washington. We then conducted a series of density gradient experiments measuring dry epiphytic biomass loss under varying mesograzer densities to test whether mesograzers consumed epiphytes, and a follow-up mesocosm experiment to observe eelgrass performance among differing snail density treatments. Our results came to the surprising conclusion that mesograzer biomass and fecal deposits had no effect on eelgrass performance. Additionally, rather than negatively impacting eelgrass performance, the amount of epiphytic cover present on the eelgrass collected in the winter from Ship Harbor, Washington was associated with increased eelgrass growth. This suggests that in some situations epiphytes may not have a negative impact on eelgrass performance. This may have significant implications for eelgrass restoration and monitoring efforts in the Salish Sea.

Eelgrass (Zostera marina) are important ecosystem engineers that provide food and habitat to diverse organisms. Some eelgrass beds are declining in locations around the Salish Sea, leading to a subsequent decline in biodiversity and productivity. One proposed restoration strategy is to transplant shoots from healthy to declining sites. Transplantation efforts, however, should consider the effects of desiccation on eelgrass during extreme low tides. Desiccation can decrease transplant success by decreasing photosynthetic rates and causing tissue damage in transplanted shoots. To understand how desiccation affects transplanted eelgrass performance, we conducted a mesocosm experiment that manipulated air exposure durations to simulate eelgrass transplantation between tidal elevations. Plants collected from three tidal heights in Ship Harbor, WA were randomly placed in tide tanks that mimicked the emersion periods of three different tidal elevations. We measured changes in eelgrass morphology, growth, and tissue damage throughout the experiment. We predicted that shoots in treatments with similar air exposure durations as their original locations would exhibit the highest growth rates and the least amount of damage. We found that eelgrass originating from a high intertidal zone that were exposed to a low intertidal treatment exhibited the least amount of bleaching damage. Neither origin nor treatment, however, affected eelgrass growth rates. Our findings suggest that transplanting shoots from the high to low intertidal zone is a useful strategy for eelgrass restoration.