Shoreline armoring disrupts marine-terrestrial connectivity in the Salish Sea, with consequences for invertebrates, fish, and birds

Within the marine-terrestrial ecotone, upper intertidal “wrack zones” accumulate organic debris from algae, seagrass, and terrestrial plant sources and provide food and shelter for many organisms. We conducted detailed surveys of wrack and log accumulations and supralittoral invertebrates in spring and fall over 3 years at 29 armored-unarmored beach pairs in Puget Sound, WA, USA. Additionally, behavioral observations of juvenile salmon (Oncorhynchus spp.) and birds were conducted at 6 pairs. Armored beaches had substantially less wrack overall, a lower proportion of terrestrial plant material in the wrack, and far fewer logs. Armored beaches had significantly fewer invertebrates and differed from unarmored beaches in their taxonomic composition. Unarmored invertebrate assemblages were dominated by talitrid amphipods and insects, and were correlated with the amount of beach wrack and logs, the proportion of terrestrial material in wrack, and the maximum elevation of the beach. Shoreline armoring influenced juvenile salmon distribution, with fewer overall observations and fish in deeper water at armored beaches, but their feeding rates were relatively high at all sites. Terrestrial birds were commonly observed foraging among beach wrack and logs at unarmored beaches, but were largely absent from armored beaches. This study demonstrates that shoreline armoring disrupts marine-terrestrial connectivity, affecting the amount and type of organic material delivered to the nearshore ecotone in the form of wrack and logs, the abundance and taxonomic composition of supralittoral invertebrates, and the distribution and behavior of secondary consumers (juvenile salmon and birds)

Effects of ocean sprawl on ecological connectivity: impacts and solutions

The growing number of artificial structures in estuarine, coastal and marine environments is causing “ocean sprawl”. Artificial structures do not only modify marine and coastal ecosystems at the sites of their placement, but may also produce larger-scale impacts through their alteration of ecological connectivity - the movement of organisms, materials and energy between habitat units within seascapes. Despite the growing awareness of the capacity of ocean sprawl to influence ecological connectivity, we lack a comprehensive understanding of how artificial structures modify ecological connectivity in near- and off-shore environments, and when and where their effects on connectivity are greatest. We review the mechanisms by which ocean sprawl may modify ecological connectivity, including trophic connectivity associated with the flow of nutrients and resources. We also review demonstrated, inferred and likely ecological impacts of such changes to connectivity, at scales from genes to ecosystems, and potential strategies of management for mitigating these effects. Ocean sprawl may alter connectivity by: (1) creating barriers to the movement of some organisms and resources - by adding physical barriers or by modifying and fragmenting habitats; (2) introducing new structural material that acts as a conduit for the movement of other organisms or resources across the landscape; and (3) altering trophic connectivity. Changes to connectivity may, in turn, influence the genetic structure and size of populations, the distribution of species, and community structure and ecological functioning. Two main approaches to the assessment of ecological connectivity have been taken: (1) measurement of structural connectivity - the configuration of the landscape and habitat patches and their dynamics; and (2) measurement of functional connectivity - the response of organisms or particles to the landscape. Our review reveals the paucity of studies directly addressing the effects of artificial structures on ecological connectivity in the marine environment, particularly at large spatial and temporal scales. With the ongoing development of estuarine and marine environments, there is a pressing need for additional studies that quantify the effects of ocean sprawl on ecological connectivity. Understanding the mechanisms by which structures modify connectivity is essential if marine spatial planning and eco-engineering are to be effectively utilised to minimise impacts

Shoreline armoring disrupts marine-terrestrial connectivity across the nearshore ecotone

Thesis (Ph.D.)--University of Washington, 2013As the interface between land and sea, the nearshore (marine-terrestrial) ecotone converges at the intertidal zone, where the exchange of organic materials between ecosystems occurs in the form of beach wrack: piles of seaweed, seagrass, and terrestrial plant debris suspended in water and deposited on shore as the tide ebbs. The ecological significance of algal and seagrass wrack subsidies has been well-documented for exposed-coast sandy beaches but is relatively unstudied in lower-energy and mixed-sediment beaches. In the nearshore ecotone where beaches are fringed with riparian vegetation, the potential for reciprocal subsidies between marine and terrestrial ecosystems exists. Human modification also occurs within this ecotone, particularly in the form of armoring structures for bank stabilization that physically disrupt the connectivity between ecosystems. I conducted detailed surveys of beach physical parameters, wrack and log accumulations, and supralittoral invertebrates in spring and fall over 3 years at 29 armored-unarmored beach pairs, and behavioral observations of juvenile salmon (Oncorhcynchus spp.) and birds at 6 pairs in Puget Sound, WA, USA. Armoring lowered the elevation of the interface between marine and terrestrial ecosystems and narrowed the width of the intertidal transition zone. Armored beaches had substantially less wrack overall and a lower proportion of terrestrial plant material in the wrack, while marine riparian zones (especially trees overhanging the beach) were an important source of wrack to unarmored beaches. Armored beaches also had far fewer logs in this transition zone. Invertebrate assemblages were significantly different between armored and unarmored beaches. Unarmored invertebrate assemblages were characterized by talitrid amphipods and adult and larval dipteran and coleopteran insects (flies and beetles, including some types that have been shown to contribute to juvenile salmon diets in other studies) and correlated with the amount of beach wrack and logs, the proportion of terrestrial material in wrack, and the maximum elevation of the beach. Shoreline type (armored or unarmored) influenced juvenile salmon distribution, however their feeding rates were relatively high at all sites, thus decreased prey availability (i.e. fewer marine riparian and/or wrack-associated insects) or altered prey resources are likely the most detrimental effects of armoring on these fish in the nearshore ecotone. Terrestrial birds, particularly Song Sparrows (Melospiza melodia) were commonly observed foraging among beach wrack and logs at unarmored beaches, but were largely absent from armored beaches. Based on my results, I developed a conceptual model summarizing marine-terrestrial connections across the nearshore ecotone and the disruptive effects of armoring. This study demonstrates that shoreline armoring disrupts marine-terrestrial connectivity, affecting the amount and type of organic material delivered to the nearshore ecotone in the form of wrack and logs, the abundance and taxonomic composition of supralittoral invertebrates, and the distribution and behavior of secondary consumers (juvenile salmon and birds). The results of my dissertation provide new information on relationships between physical and biological variables in the nearshore ecotone and connections between marine and terrestrial ecosystems that may be useful in informing conservation, restoration, and management actions

Olympic Sculpture Park: Year 3 monitoring of shoreline enhancements

In January 2007 the Seattle Art Museum’s Olympic Sculpture Park (OSP) opened at a site along Seattle’s urbanized Elliott Bay shoreline. The park includes enhanced shoreline features designed to benefit juvenile salmon and other organisms. A pocket beach and habitat bench were created in shallow nearshore waters, vegetation was planted in the uplands, and coarse‐grained sediments and driftwood were placed on the beach. These features replaced the relatively unproductive armored seawall and riprap shoreline, with a goal of increasing the number and diversity of fish and invertebrates. Although this shoreline is in an urban, commercial setting and will not be completely restored to pre‐historic conditions, the park has enhanced a publically accessible segment of shoreline that has more natural functions than it did before.Seattle Public Utiltie

The impacts of armoring on Salish Sea beaches: overview, background, and methods

Shoreline armoring is widespread in the Salish Sea, but few data have documented actual impacts on physical or biological features of local nearshore ecosystems. Armoring marine shorelines can alter natural processes at multiple spatial and temporal scales; some, such as ‘starving’ the beach of sediments, may take decades to become visible, while others such as ‘placement loss’ are immediate. Two research teams have been studying a broad set of sites to document parameters that do and do not change when a shoreline is armored, and to determine under what conditions armoring has significant effects. Our methodology has been to compare paired adjacent armored and unarmored beaches. During the years 2010 - 2013 we completed surveys at 6 pairs of beaches in South Sound, 25 pairs in Central Sound, and 36 pairs in the North. At all sites we have data on habitat and setting (e.g., overhanging vegetation, location in the drift cell); beach topography; sediment size distributions; abundance and types of logs, wrack, and invertebrates in the wrack line; and juvenile clams at Mean Low Water. At some sites we have data on forage fish spawn. Overall, demonstrating physical differences between paired beaches is difficult given the very high natural variability among beaches, although obvious effects such as reduction in beach width are evident. Limited data show that wave heights are greater where they interact with armoring, and beach slope near the armoring tends to steepen. Many biological effects are clear at the upper part of the beach, while lower elevation effects (further from armoring) are progressively harder to demonstrate. Armoring impacts are less dramatic at the pairs of beaches in the northern Salish Sea. There does not appear to be a distinct threshold in elevation of armoring that causes increased impacts, but instead a gradient. Analyses of these diverse datasets are ongoing, and results are detailed in the following linked presentations

Climate Is Variable, but Is Our Science?

Peer Reviewe