Resource Management 2 Lecture 6 (Part 2) Notes for 2024 PDF

Resource Management 2 (Lecture 6: Part 2) Cowardin Wetland Classification Estuarine Wetland Systems  Estuarine Wetland Systems  The estuarine wetland system consists of deepwater tidal habitats and adjacent tidal wetlands that are usually semi- enclosed by land but have open, part...

Resource Management 2 (Lecture 6: Part 2) Cowardin Wetland Classification Estuarine Wetland Systems  Estuarine Wetland Systems  The estuarine wetland system consists of deepwater tidal habitats and adjacent tidal wetlands that are usually semi- enclosed by land but have open, partly obstructed, or sporadic access to the open ocean  In the estuarine wetland system, ocean water is at least occasionally diluted by freshwater runoff from the land  Estuarine Wetland Systems  The estuarine wetland system includes both estuaries and lagoons  Estuarine Wetland Systems  The estuarine wetland system is more strongly influenced by its association with land  In terms of wave action, estuaries are generally considered to be low-energy systems (Chapman, 1977) The salinity may be periodically increased above that of the open ocean (hyperhaline) after long periods of evaporation or little salinity (oligohaline) during events likes hurricanes Along some low-energy coastlines there is appreciable dilution of sea water Oblique aerial photo of the lower portion of the Mgobezeleni floodplain and estuary, Northern KwaZulu-Natal after the high seas of March 2007 had caused an inflow of saline water which killed the sedge swamp and several of the large Ficus trichopoda trees. Source: Taylor (2016)  Estuarine Wetland Systems  Estuarine water regimes and water chemistry are affected by the following factors Oceanic tides Precipitation Freshwater runoff from land areas Evaporation Wind The salinity of an estuary can vary dependent on the amount of freshwater inflows, as well as, the tidal movement and location within the estuary. Estuarine salinities are classified according to the Venice Classification. Source: Montagna et al. (2013) Estuarine salinities according to the Venice Classification Freshwater conditions are < 0.5 ppt Oligohaline conditions occur when the salinity ranges between 0.5 – 4.9 ppt Mesohaline waters have a salinity range between 5.0 – 17.9 ppt Polyhaline conditions range from 18.0 – 29.9 ppt Euhaline are saline conditions ranging between 30.0 – 35.9 ppt Hypersaline are saline conditions ≥ 36 ppt Source: Little et al. (2022) Location of the Great Fish Estuary in the Eastern Cape Province of South Africa and a map divided into salinity zones according to the Venice Classification, with the positions of stationary receivers (automatic listening station, ALS-1 to ALS-11) and pressure and temperature loggers. Source: Næsje et al. (2012) Overview of definitions and morphological elements indicated on the estuary of Whitehaven beach, Australia. Source: Leuven (2014)  Boundaries of Estuarine Wetland Systems  The estuarine wetland system in the Cowardin classification is defined by its unique position at the interface of tidal influence, salinity gradients and the mixing of freshwater and marine waters  The boundaries of the estuarine wetland system are determined by various hydrological, ecological and physical characteristics, which are crucial for identifying, managing and conserving these important ecosystems  The estuarine system also includes offshore areas of continuously diluted sea water  Boundaries of Estuarine Wetland Systems  The estuarine wetland system extends From the landward boundary (upper reaches of the tide, where oceanic saltwater meets the shore) To the seaward boundary (where estuarine waters transition to marine waters, often marked by a reduction in freshwater influence and increased salinity resulting in brackish water conditions)  It includes areas From the mean high-water mark, extending upstream and landward to where salinity measures less than 0.5 ppt and tidal influence is reduced Of an imaginary line closing the mouth of a river or bay  Boundaries of Estuarine Wetland Systems  These boundaries delineate the extent of estuarine wetland systems and are crucial for understanding their ecological dynamics and management  These boundaries are critical for the conservation, management and study of estuarine wetland systems, ensuring their ecological integrity and sustainability  Horizontal Boundaries of Estuarine Wetland Systems Landward Boundary The landward boundary of the estuarine wetland system extends to the upper reaches of tidal influence, where oceanic saltwater penetrates inland This is typically marked by the mean high-water line along the coast It includes areas where freshwater from rivers, streams or other inland water bodies mixes with saltwater from the ocean This mixing creates brackish water conditions characteristic of estuarine environments The landward boundary can extend further inland in areas where saltwater intrusion occurs due to low freshwater input or rising sea levels Seaward Boundary The seaward boundary is defined where estuarine waters transition into the more saline waters of the marine wetland system This boundary is often marked by a reduction in freshwater influence and increased salinity levels In many cases, this boundary aligns with the mean low-water line along open coastlines or barrier islands that separate estuaries from the open ocean Natural features such as barrier islands, spits and sandbars can serve as physical markers of the seaward boundary  Vertical Boundaries of Estuarine Wetland Systems Subtidal Boundary The subtidal zone includes areas that are continuously submerged under water, extending from the low tide mark to deeper areas within the estuary Includes subtidal channels, submerged parts of tidal flats and deeper parts of estuarine bays Intertidal Boundary The intertidal zone lies between the mean high-water and mean low-water marks, experiencing regular exposure and submersion due to tidal cycles Includes tidal marshes, mudflats and mangrove swamps, which are regularly influenced by tidal action  Ecotones of Estuarine Wetland Systems Ecotones in estuarine wetland systems are transition zones where freshwater from rivers and streams meets saltwater from the ocean, creating highly dynamic and productive habitats Estuaries are among the most biologically diverse ecosystems, supporting a wide range of plant and animal species adapted to fluctuating salinity levels, tidal influence and nutrient- rich waters Ecotones within estuarine wetlands are critical for biodiversity, nutrient cycling and coastal resilience Protecting and conserving these transition areas is essential for maintaining the health and resilience of estuarine ecosystems in the face of environmental change Riverine-Estuarine Ecotone This ecotone marks the transition between freshwater riverine systems and saline estuarine environments It is characterized by gradients in salinity, sediment deposition and water flow Vegetation in this zone includes species adapted to both freshwater and brackish conditions, such as marsh grasses and submerged aquatic plants The riverine-estuarine ecotone serves as a nursery habitat for fish and invertebrates and facilitates the exchange of nutrients between riverine and estuarine ecosystems  Ecotones of Estuarine Wetland Systems Intertidal Mudflat/Sandflat Ecotone Along the shoreline of estuarine wetlands, the intertidal mudflat or sandflat ecotone is a dynamic zone subject to tidal inundation and exposure Mudflats and sandflats are characterized by soft sediments and support unique assemblages of burrowing organisms, including worms, clams and crabs Shorebirds and wading birds forage in these areas during low tide, feeding on invertebrates and small fish Salt Marsh Ecotone Salt marshes are dominant features of many estuarine wetland systems The salt marsh ecotone represents the transition between unvegetated tidal flats and the dense vegetation of the salt marsh It provides important habitat for marsh-edge species and helps stabilize shorelines by trapping sediments and dissipating wave energy Tidal Creek/Channel Ecotone Tidal creeks and channels are narrow, meandering waterways that intersect estuarine wetlands, connecting them to the main channel of the estuary The tidal creek ecotone is characterized by fluctuating water levels, sediment transport and nutrient exchange It supports diverse communities of aquatic organisms, including fish, shrimp and oysters, and provides essential nursery habitat for juvenile species  Ecotones of Estuarine Wetland Systems Brackish Water Marsh-Mangrove Ecotone In estuaries where freshwater and saltwater mix, the brackish water marsh-mangrove ecotone forms This transitional zone supports a mosaic of vegetation, including salt-tolerant grasses, shrubs and mangrove trees It provides important habitat for a variety of estuarine species and serves as a buffer against coastal erosion and storm surge  Factors influencing Boundaries of Estuarine Wetland Systems Tidal Influence The extent of the intertidal zone can vary significantly with the tidal range Areas with high tidal ranges will have larger intertidal zones compared to areas with low tidal ranges Spring tides (with greater tidal range between high and low tides) and neap tides (with smaller tidal range between high and low tides) also cause periodic changes in the boundaries of estuarine wetlands Freshwater Input Seasonal variations in river flow due to rainfall, snowmelt or drought can increase or decrease the estuarine zone High river flows can push the saltwater boundary seaward, while low flows can allow saltwater to penetrate further inland Human activities such as damming, irrigation and water extraction can alter the flow of freshwater into estuarine systems, affecting their boundaries Sea Level Changes Long-term sea level rise due to climate change can lead to the landward migration of estuarine boundaries, inundating previously terrestrial or freshwater areas Short-term events like storm surges can temporarily alter the extent of estuarine systems, causing saltwater intrusion into freshwater areas  Factors influencing Boundaries of Estuarine Wetland Systems Geomorphology The shape and slope of the land influence how far tidal waters can penetrate inland Flat, low-lying areas will have broader estuarine zones compared to steep, rocky coasts Natural processes of sediment deposition (building up of land) and erosion (wearing away of land) can change the shape and extent of estuarine wetlands Salinity Gradients The location of the mixing zone where freshwater and saltwater mix can shift due to changes in freshwater inflow or tidal dynamics, affecting the extent of brackish conditions that define estuarine wetlands Seasonal changes in temperature and evaporation rates can influence salinity levels and the boundaries of estuarine zones Human Activities Urbanization, agriculture and industrial activities near estuaries can alter natural water flows and sedimentation patterns, impacting estuarine boundaries The construction and presence of dikes, levees, sea walls and other coastal defenses can artificially fix or alter the boundaries of estuarine systems, affecting hydrology and ecosystem dynamics Human activities such as damming, water diversion and construction of tidal barriers can alter the natural boundaries of estuarine systems  Accurate Delineation of Estuarine Wetland System Boundaries is crucial for several reasons Ecological Importance Estuarine wetland systems support diverse ecosystems with unique flora and fauna adapted to brackish water conditions. Accurate delineation ensures the protection of these habitats, which are often hotspots of biodiversity. Many commercially and ecologically important fish and shellfish species rely on estuarine wetlands for spawning, nursery and feeding grounds. Clear boundaries help protect these critical habitats. Estuarine wetland systems act as natural buffers against coastal erosion, storm surges and flooding, providing essential protection for coastal communities and infrastructure. Estuarine wetlands improve water quality by filtering pollutants, trapping sediments and removing excess nutrients from runoff and tidal waters.  Accurate Delineation of Estuarine Wetland System Boundaries is crucial for several reasons Resource Management Estuarine wetland systems provide important habitat for biota that support commercial and recreational fisheries. Accurate delineation helps manage these fisheries sustainably by protecting critical spawning and nursery areas. Estuarine wetlands may also support shellfish aquaculture operations. Clear boundaries ensure that aquaculture activities are properly sited and managed to minimize environmental impacts. Accurate delineation of estuarine wetland system boundaries guide coastal development and land use planning, helping to avoid conflicts with sensitive habitats and ecosystems. Understanding the extent of estuarine wetland systems is crucial for assessing coastal hazards, such as sea-level rise, erosion and saltwater intrusion, and developing effective adaptation and mitigation strategies.  Accurate Delineation of Estuarine Wetland System Boundaries is crucial for several reasons Legal and Regulatory Compliance Many countries have laws and regulations aimed at protecting estuarine wetland systems due to their ecological significance. Accurate delineation ensures compliance with these laws, preventing unauthorized development or degradation of wetland areas. Estuarine wetlands are often included within designated Marine Protected Areas (MPAs) or coastal management zones. Clear boundaries are essential for enforcing regulations and managing human activities within these protected areas. Socio-Economic Benefits Estuarine wetland systems attract tourists interested in birdwatching, kayaking, fishing and other outdoor activities. Protecting these areas through accurate boundary delineation supports sustainable tourism and local economies. Estuarine wetlands provide opportunities for environmental education and outdoor recreation, enhancing public awareness and appreciation of coastal ecosystems. Many estuarine wetlands have cultural and historical significance for indigenous and local communities and the accurate delineation helps protect these cultural values and ensures that traditional uses are respected.  Accurate Delineation of Estuarine Wetland System Boundaries is crucial for several reasons Scientific Research and Monitoring Accurate boundaries provide a consistent framework for monitoring changes in estuarine wetland systems over time, including habitat loss, water quality degradation and species distributions. Researchers rely on precise delineation to study the ecological processes, species interactions and ecosystem functions within estuarine wetlands. Idealized map of a typical estuary showing three divisions, lower, middle and upper estuary. The boundaries are transition zones that shift according to season, weather, tidal range and river discharge. Source: Fairbridge (1980) Salomens and Forstner (1984) Schematic structure of an estuary. Boundaries between reaches may change in position depending on river discharge and tidal range. Source: Perillo (1995) Charente Estuary, French Atlantic Coast (Google Earth image). Columbia River Estuary, US Pacific Coast (Google Earth image). Dyfi Estuary, Wales, Irish Sea (Google Earth image). Western Scheldt and Scheldt Estuary, Netherlands and Belgium (Sentinel image). Subsystems of Estuarine Wetland Systems Subtidal Areas that are continuously submerged under tidal water This zone includes subtidal channels, submerged 01 marshes and seagrass beds It is characterized by high nutrient availability and diverse aquatic life Examples include submerged portions of estuarine channels and estuarine bays Intertidal Areas that are exposed and flooded by tides, lying 02 between the mean high-water and mean low-water marks, includes the associated splash zone This zone includes mudflats, tidal marshes and mangrove swamps, it supports a variety of plant and animal species adapted to periodic inundation and exposure Examples include salt marshes, tidal creeks and intertidal mudflats  Classes of Estuarine Wetland Systems  Rock Bottom, Unconsolidated Bottom, Aquatic Bed, Reef, Streambed, Rocky Shore, Unconsolidated Shore, Emergent Wetland, Scrub-Shrub Wetland and Forested Wetland  Distinguishing features and examples of habitats in estuarine wetland systems. EHWS is extreme high water of spring tides, ELWS is extreme low water of spring tides. Source: Cowardin et al. (1979)  Ecological Significance of Estuarine Wetland Systems Biodiversity and Habitat Estuarine wetland systems support a rich diversity of plant and animal species, including many that are specially adapted to the brackish water environment where freshwater and seawater mix They provide essential habitats for a wide range of organisms, including fish, invertebrates, birds and mammals Many species use estuarine wetlands as breeding, feeding and nursery grounds These wetlands often host species that are found nowhere else, making them critical for the conservation of endemic species Many estuarine wetlands are home to threatened or endangered species and their protection is vital for preventing extinctions  Ecological Significance of Estuarine Wetland Systems Ecosystem Services Estuarine wetland systems act as natural buffers, absorbing wave energy and reducing the impact of storms and coastal erosion Salt marshes and mangroves, in particular, help protect shorelines from storm surges and rising sea levels These wetlands trap and stabilize sediments, which can help prevent coastal erosion and maintain water clarity Estuarine wetlands play a crucial role in filtering and trapping pollutants, including excess nutrients, heavy metals and sediments, from rivers before they reach the ocean This filtration helps maintain water quality and supports the health of coastal marine ecosystems They can remove toxic substances from water through natural filtration processes, thereby reducing pollution levels and improving the overall health of coastal waters  Ecological Significance of Estuarine Wetland Systems Carbon Sequestration Estuarine wetlands, particularly mangroves and salt marshes, are highly efficient at capturing and storing carbon They sequester large amounts of carbon in their biomass and soils, helping to mitigate climate change The carbon stored in estuarine wetland systems can remain sequestered for centuries if undisturbed, making them critical components in global carbon management strategies Hydrological and Nutrient Regulation Estuarine wetland systems regulate water flow and contribute to the hydrological cycle They help in maintaining groundwater levels and reducing the severity of floods by absorbing excess water during heavy rains These wetlands play a key role in the redistribution of nutrients, supporting primary productivity in coastal and marine ecosystems Fishery and Food Resources Many marine species, including commercially important fish and shellfish, depend on estuarine wetland systems for breeding, spawning and as nurseries for their young This makes these wetlands crucial for sustaining fishery resources The high productivity and biodiversity of estuarine wetlands contribute to robust and resilient fisheries, supporting local economies and food security  Ecological Significance of Estuarine Wetland Systems Cultural and Recreational Value Estuarine wetland systems have significant cultural value for many coastal communities, providing resources for traditional practices and livelihoods They often contain cultural heritage sites and are integral to the cultural identity and heritage of indigenous and local populations These ecosystems are popular destinations for ecotourism and recreational activities such as birdwatching, fishing and kayaking Their scenic beauty and biodiversity attract tourists, contributing to local economies Estuarine wetlands serve as natural laboratories for scientific research and environmental education, helping to raise awareness about the importance of conserving these ecosystems Climate Regulation Estuarine wetland systems help moderate local temperatures and create microclimates that can benefit nearby terrestrial ecosystems and human communities By influencing weather patterns, estuarine wetlands can play a role in reducing the intensity of extreme weather events