20% More Eelgrass in Puget Sound by 2020: Restoration Site Selection

As part of a larger program by the state of Washington to restore the Puget Sound ecosystem, we are engaged in a selection process to locate specific areas where eelgrass could be restored or enhanced to meet the goal of 20% more eelgrass by 2020, amounting to a ~4,000 ha increase in areal eelgrass coverage. Embedded in this goal is the establishment and development of meadows that are resilient to the effects of climate change and anthropogenic and natural disturbances. We hypothesize that: (1) many sites are recruitment limited; (2) eelgrass has been lost in some areas because of temporary disturbance; and (3) there may be broader stresses limiting eelgrass in subregions of Puget Sound. Our approach utilizes an understanding of eelgrass growth requirements coupled with hydrodynamic and water quality models, an eelgrass growth model, field observations, and test plantings. We are using these results along with spatial data and stressor information collected as part of regional assessments of nearshore ecosystem condition to identify restoration sites. We are also working with local governments to determine actions that could be taken to improve conditions for eelgrass within their jurisdictions to maximize the success and long-term viability of planted meadows. The models revealed differences in the predicted growth rate of eelgrass among regions. In general, northern Puget Sound and Strait of Juan de Fuca provided the best conditions, whereas Hood Canal and southern Puget Sound were relatively less suitable for eelgrass. Field visits were conducted at 23 sites where the eelgrass model predicted good growing conditions but where eelgrass does not presently exist based on available information. From among these sites we selected five sites for test planting. Test plantings, modeling and jurisdictional information will form the basis to develop strategies for larger recovery efforts

Mimicry of emergent traits amplifies coastal restoration success

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A plastochrone method for measuring leaf growth in eelgrass, Zostera marina L

Eelgrass, Zostera marina L., leaf growth measurement methods were investigated and compared in New Hampshire and Maine, USA. The commonly used leaf marking method, developed by Zieman (1974) and embraced by Dennison (1990), was found to underestimate leaf growth, particularly when measured over small time intervals, compared to a method developed by Short (1987) based on the weight of mature leaf tissue. Short\u27s method (1987) was then compared to a modification of the plastochrone interval method of Jacobs (1979), giving very similar results. In our plastochrone method, leaf growth is calculated as the weight of a mature leaf divided by the time interval between initiation of two successive leaves on one shoot, the plastochrone interval. Our investigations demonstrate that the leaf plastochrone interval in eelgrass varies seasonally; to use the plastochrone method, the plastochrone interval must be measured for each growth determination. Based on our comparisons, we recommend what we call the \u27plastochrone method\u27 as a more efficient and accurate way to measure eelgrass leaf growth

Occurrence of Halophila baillonii meadows in Belize, Central America

Halophila baillonii Ascherson was found in Belize, Central America in 2003 and 2005. The observation extends the known range of this seagrass species to the western Caribbean. H. baillonii was previously recorded only in the eastern Caribbean and at one Pacific site in Panama. Both fruits and flowers of H. baillonii were observed at two locations in Belize in 2005. H. baillonii in Belize is an important food for manatee, forms a productive seagrass-based ecosystem, and is adversely affected by shoreline development and watershed run-off

Sheath length as a monitoring tool for calculating leaf growth in eelgrass (Zostera marina L.)

Recent advances have improved ease and accuracy in seagrass growth measurements. Despite these improvements, seagrass leaf growth can be difficult to measure effectively; current methods are destructive to the plants and require at least two site visits per growth period. We used the “previous growth” of Ibarra-Obando and Boudouresque [Ibarra-Obando, S.E., Boudouresque, C.F., 1994. An improvement of the Zieman leaf marking technique for Zostera marina growth and production assessment. Aquat. Bot. 47, 293–302.] to develop a relationship between sheath length and leaf growth in eelgrass, Zostera marina L., and we demonstrated that a simple, non-destructive method allows reliable calculation of eelgrass leaf growth (mg shoot−1 day−1) based on sheath length. We measured eelgrass sheath length and leaf growth for 18 months, from November 1999 to April 2001, at a site in Portsmouth Harbor on the border of New Hampshire and Maine, USA. Regression analyses showed a high coefficient of determination between sheath length and leaf growth, demonstrating that sheath length reliably reflected eelgrass leaf growth. We also showed that four seasonal measurements were sufficient to establish a significant relationship between sheath length and leaf growth. After a regression of sheath length and leaf growth has been established for a site, eelgrass sheath length can be measured in situ to accurately calculate leaf growth, eliminating both the need for destructive growth measurements and the need to mark and relocate plants

SeagrassNet monitoring across the Americas: case studies of seagrass decline

Seagrasses are an important coastal habitat worldwide and are indicative of environmental health at the critical land–sea interface. In many parts of the world, seagrasses are not well known, although they provide crucial functions and values to the world\u27s oceans and to human populations dwelling along the coast. Established in 2001, SeagrassNet, a monitoring program for seagrasses worldwide, uses a standardized protocol for detecting change in seagrass habitat to capture both seagrass parameters and environmental variables. SeagrassNet is designed to statistically detect change over a relatively short time frame (1–2 years) through quarterly monitoring of permanent plots. Currently, SeagrassNet operates in 18 countries at 48 sites; at each site, a permanent transect is established and a team of people from the area collects data which is sent to the SeagrassNet database for analysis. We present five case studies based on SeagrassNet data from across the Americas (two sites in the USA, one in Belize, and two in Brazil) which have a common theme of seagrass decline; the study represents a first latitudinal comparison across a hemisphere using a common methodology. In two cases, rapid loss of seagrass was related to eutrophication, in two cases losses related to climate change, and in one case, the loss is attributed to a complex trophic interaction resulting from the presence of a marine protected area. SeagrassNet results provide documentation of seagrass change over time and allow us to make scientifically supported statements about the status of seagrass habitat and the extent of need for management action

Eelgrass Resilience and Climate Change in Puget Sound

To what degree will climate change affect seagrass productivity, abundance and distribution in Puget Sound and other northwest systems? While the widespread global distribution of eelgrass and its ability to recover from large-scale disturbances suggests a relatively high level of adaptability and resilience, complex ecological interactions make reliable predictions of the effect of climate variation and change on eelgrass difficult. We have been using field measurements of density and growth rate over several decades, physiological experiments, and numerical modeling coupled with natural experiments associated with anomalous climatic and ocean conditions to formulate broad hypotheses. These data have shown that: (1) inter-annual variation in growth, density and biomass is affected by variable sea level, water temperature and light conditions; (2) these interactions are complex and dependent upon the system; (3) highly anomalous conditions (e.g., ENSO; droughts) that persist for more than one year may drive a system-wide collapse of eelgrass to a point were recovery is severely protracted; (4) local disturbances (e.g., eutrophication; turbidity; grazing) can interact with climate variation to exacerbate unfavorable conditions; and, (5) success of efforts to restore eelgrass may be hampered by a severely altered system state. We conclude that eelgrass is resilient to moderate to strong climatic variations lasting a few years, but is susceptible to collapse and extirpation when extreme, unprecedented climatic conditions persist over a similar time period

Mimicry of emergent traits amplifies coastal restoration success

Restoration is becoming a vital tool to counteract coastal ecosystem degradation. Modifying transplant designs of habitat-forming organisms from dispersed to clumped can amplify coastal restoration yields as it generates self-facilitation from emergent traits, i.e. traits not expressed by individuals or small clones, but that emerge in clumped individuals or large clones. Here, we advance restoration science by mimicking key emergent traits that locally suppress physical stress using biodegradable establishment structures. Experiments across (sub)tropical and temperate seagrass and salt marsh systems demonstrate greatly enhanced yields when individuals are transplanted within structures mimicking emergent traits that suppress waves or sediment mobility. Specifically, belowground mimics of dense root mats most facilitate seagrasses via sediment stabilization, while mimics of aboveground plant structures most facilitate marsh grasses by reducing stem movement. Mimicking key emergent traits may allow upscaling of restoration in many ecosystems that depend on self-facilitation for persistence, by constraining biological material requirements and implementation costs