Appendix B Wells Harbor Ecology (Materials from the Wells NERR)

APPENDICES Appendix B Wells Harbor Ecology (materials from the Wells NERR) CHAPTER 8 Vegetation Caitlin Mullan Crain lants are primary producers that use photosynthesis ter). In this chapter, we will describe what these vegeta- to convert light energy into carbon. Plants thus form tive communities look like, special plant adaptations for Pthe base of all food webs and provide essential nutrition living in coastal habitats, and important services these to animals. In coastal “biogenic” habitats, the vegetation vegetative communities perform. We will then review also engineers the environment, and actually creates important research conducted in or affiliated with Wells the habitat on which other organisms depend. This is NERR on the various vegetative community types, giving particularly apparent in coastal marshes where the plants a unique view of what is known about coastal vegetative themselves, by trapping sediments and binding the communities of southern Maine. sediment with their roots, create the peat base and above- ground structure that defines the salt marsh. The plants OASTAL EGETATION thus function as foundation species, dominant C V organisms that modify the physical environ- Macroalgae ment and create habitat for numerous dependent Algae, commonly known as seaweeds, are a group of organisms. Other vegetation types in coastal non-vascular plants that depend on water for nutrient systems function in similar ways, particularly acquisition, physical support, and seagrass beds or dune plants. Vegetation is reproduction. Algae are therefore therefore important for numerous reasons restricted to living in environ- including transforming energy to food ments that are at least occasionally sources, increasing biodiversity, and inundated by water. Because algae creating habitat. photosynthesize using light reflected through the water, most algae cannot Major vegetation types in the coastal live in dark ocean depths and thus areas of Wells NERR include mac- are most common in intertidal and roalgae, submerged aquatic vegeta- shallow subtidal environments. Algae tion, and beach dune communities, are generally broken into three major and marshes (which vary in salinity divisions based on their photosynthetic from salt to brackish to tidal freshwa- 85 pigments—red, green, and brown—which are used for algae provide a food source for numerous invertebrates identification and characterization. and an anchoring site for other epiphytic algae (see kelp fronds pictured). Knotted wrack and rockweed are criti- Species diversity of algae is high on southern Maine cal rocky shore organisms, responsible for much of the coastlines, with 148 species of seaweeds recorded in intertidal productivity and habitat provisioning of these coastal and estuarine environments (Mathieson et al. shores. These macroalgae are harvested for packing ma- 2001). While many species can be found in this region, terial in the shellfish industry which can locally threaten coastal habitats defined by algal occupants are less macroalgal populations, particularly since reproductive common. Macroalgal communities are dominant on output is relatively low and localized. hard substrate, particularly rocky shores. In southern Maine, the shoreline is predominantly soft sediments These dominant brown algae can also be found grow- and macroalgae persists here on occasional hard sub- ing without holdfasts in the low salt marsh community strates or in un-anchored forms. Hard substrates on this (Mathieson and Dawes 2001, pictured). Here the algae stretch of coast are typically man-made structures such are effectively anchored by growing entangled in and as docks or jetties, or occasional boulders. These sub- around the roots and shoots of the salt marsh plants. strates are often colonized by large brown algae, knotted Research has shown that both plants and algae benefit wrack, Ascophyllum nodosum, rockweed, Fucus vesiculosus from this association as the plants are more productive, or Fucus spiralis. These same habitats can be opportunis- likely due to algal nutrient delivery, and the algae gain tically occupied, particularly after disturbances or when anchor sites and are less subject to desiccation (Gerard herbivory by snails is low, by fast growing green algae 1999). Enteromorpha intestinalis and Ulva lactuca. The macroalgal communities have been well studied in their more Non-anchored macroalgae can also be found free-floating extensive ranges on rocky shorelines, but their role here in the water column as drift algae. Most drift algae origi- is likely very similar. Mats of large brown algae have been nate as attached plants that are disturbed, often resulting shown to alter local environmental conditions by provid- in altered morphology and loss of sexual reproduction. A ing a cool, moist habitat favored by many invertebrate high diversity of algal species can be found as drift algae. species that are otherwise limited from these locations High nutrients in the water column, often due to human by dessication stress (Bertness et al. 1999). Intertidal sources, can cause “blooms” of drift algae which can be quiet harmful to the marine environment, by causing low oxygen conditions, fouling beaches, impacting fisheries and altering marine communities. Submerged Aquatic Vegetation (SAV) Submerged aquatic vegetation (SAV), commonly known as seagrass, are rooted flowering plants (angiosperms) that are specially adapted for surviving life underwater. Subtidal seagrass beds are very productive, supplying food and carbon to adjacent marine communities, and provide habitat and predator refuge to numerous asso- ciated invertebrate and fish species. Seagrass beds trap and bind sediments, preventing coastal erosion and driv- ing geomorphology of the shoreline. Beds of eelgrass, “Ecads,” a type of algae that become entangled among salt marsh plants and then continue to grow, are the topic of Zostera maritima, were common historically in shallow a 2006 research project at Wells NERR. Note the PVC coastal areas of New England, but their areal coverage tubing marking a research plot, and the grey-blue algae has declined due to nutrient pollution, physical distur- at the base of the green Spartina alterniflora. Photo bance and disease. These communities are very impor- Megan Tyrrell. tant for marine health and substantial efforts have been 86 Wells National Estuarine Research Reserve Kelp fronds anchored by a holdfast to a cobble. Photo Susan Bickford. directed towards seagrass restoration projects in New salinities and shifting sediments. Many of these plants England. While seagrass beds are not currently found have similar adaptations for dealing with high salinities within Wells NERR, there is some indication that the and water stress as will be described in the salt marsh subtidal mudflats were once colonized by eelgrass (Short plants below, such as succulence, sunken stomates and et al. 1992). curled or hairy leaves. These plants are additionally adapted to grow quickly after burial by sand. SAV can also be found in permanent ponds within salt marshes. Widgeongrass, Ruppia martima, is common As the dune ages, plant roots increase stability and in- and abundant and can tolerate the variable and at times crease organic matter, making nutrients more available. harsh conditions of these marsh pools. Widgeongrass is Dunes thus exhibit stages of succession that are mir- a favorite and important food source for ducks and wa- rored by zonation of plants that vary in their ability to terfowl that pause along migratory routes to fuel up in tolerate the varying physical conditions. Typical dune salt marsh ponds. succession is characterized with increasing age by the foredune community, dunegrass community (pictured), Dune Vegetation dry dune slack community, shrub community and dune Coastal dunes form above the highwater line of sandy forest community (Nelson and Fink 1980). Each com- beaches and define the terrestrial edge of these habitats. munity has characteristic plants adapted to the physical Dunes are dynamic communities that are colonized conditions and facilitated by plants and their feedbacks and stabilized by plants, and through succession can be in earlier successional stages. transformed to more terrestrial environments or can be eroded and return to the sea. Dunes result from onshore The dominant plant species on foredunes of southern winds that blow sand particles up the shoreline until Maine is beach grass, Ammophila breviluguilata. Other they are deposited and stabilized, usually by wrack, at plants often found in the dunes include dusty miller, the high tide line. These “embryo” dunes are unstable Artemesia stelleriana, and beach pea, Lathyrus japonicus. and transient unless colonized by plants. Dune plants Dune vegetation is responsible for stabilizing and creat- are specially adapted to these variable conditions, and ing the developing dune community which is an impor- primary colonizers are tolerant of dry conditions, high tant habitat for other wildlife. Of particular importance Vegetation 87 American beachgrass at the edge of a dune at Laudholm Beach. Photo Hannah Wilhelm. in southern Maine is provision of habitat to endangered seabirds, least terns and piping plovers. Dune communities are present on the Laudholm Beach where the natural dune remains. However, much of the dune habitat in southern Maine has been removed due to coastal development. Loss of dunes makes shorelines less stable and removes the wave buffering capacity, making coastal habitats much more vulnerable

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