ENVSCI 702 : Applied Estuarine Ecology
2021 Semester Two (1215) (15 POINTS)
We are focused on estuaries as these ecosystems have been crucial to the development of our species, but dominated by soft-sediment habitats they also provide us with and easy place to ask and test some important questions that relate to the structure and function of the most common seafloor habitat.
Estuaries are complex ecological systems that mark the transition between freshwater and the open coast. They cover a diverse cross-section of habitats supporting a wide range of human activities and values and are an integral part of the cultural identity of New Zealanders. Estuaries are transitional environments, the meeting place of land, freshwater and marine ecosystems.
New Zealand has an extensive shoreline (about 18 000 km) that includes more than 400 estuaries, collectively covering about 5300 km2. The transitional nature of estuaries makes them hard to define, but they are generally considered to be tidally influenced water bodies largely enclosed by land in which there is a measurable dilution of seawater due to freshwater inputs from rivers and runoff. Thus all of our harbours and much of our iconic coastline are, by definition, estuaries. New Zealand’s estuaries have a wide diversity of coastal geomorphological forms ranging from the fiords of southwestland (e.g., Doubtful Sound), to drowned river valleys (e.g., Hokianga Harbour), to lagoons (e.g., Okarito). Our biggest harbours are Kaipara and Manukau, although much of the Hauraki Gulf can also be defined as an estuary. Areas within estuaries that fall between the high and low tide marks are exposed and inundated during the rise and fall of the tide. These intertidal flats and reefs are particularly important to ecological processes in estuaries and often occupy a large part of the estuary.
Biodiversity and ecosystem services are intimately linked. Biodiversity encompasses the variety of life and its interaction with the environment, ranging from genotypes to ecosystems. Dominated by marine organisms, our estuaries are diverse and contain representatives of a wide range of phyla from micro-organisms to whales. On the intertidal sandflats of the estuaries around Auckland we can easily collect 200 species of organisms big enough to see with the naked eye. By marine standards estuaries are generally considered species poor ecosystems. Nevertheless, the resident species, the strong physical and chemical gradients found within estuaries and the supply of nutrients from the adjacent catchment make estuaries functionally diverse
Across New Zealand, the range of habitats found on the floor of estuaries is tremendous, from the terrestrial fringing habitats of saltmarsh and mangrove to the deep-water muddy basins at the bottom of the fiords. There is more to the description of estuary habitats than rock, sand and mud. Just like terrestrial habitats, estuarine habitats are most informatively defined based on dominant and habitat structuring species. These habitats can include tube mats, scallop beds, oyster reefs, crab burrowed mudflats, cockle beds, mussel beds, sponge gardens, kelp reefs and turfing algae. These descriptive habitat designations often give us clues as to dominant ecological.
Many species fundamentally influence ecosystem processes by altering the physical architecture of the sediment. Organisms and their burrows, mounds and tubes, modify flow over the seafloor and provide settlement sites and refugia from predators. On the sediment surface, predators (e.g., rays, birds, fish, starfish and crabs) digging into the sediment in search of food create pits, adding to the heterogeneity of the seafloor, while microscopic algae bind the sediment surface and the movement of animals crawling over the surface affect sediment erodability. Below the sediment surface, physical structures such as tubes and burrows and the activities of animals that affect the movement of particles and pore water, influence habitat heterogeneity and many important microbial and geochemical processes. Microbes in the sediments drive nutrient and carbon cycling, but this is strongly facilitated by the movement, burrowing, hydraulic pumping and feeding of animals living both on (epifaunal) or within (infauna) the sediment. These processes highlight important links between seabed and water-column ecosystems that affect nutrient recycling, the processing of organic material and carbon storage.
Collectively the activities of estuarine organisms significantly influence the nature and rate of biogeochemical processes that sustain the biosphere. The shallow comparatively warm, sunlit, well mixed waters and extensive soft-sediment habitats of estuaries are often considered to play significant roles in processing contaminants from land and fuelling productivity on the adjacent coast. Fish live within and pass through estuaries, either to spawn in rivers, or to spend their adulthood in the open sea.
Most of our major cities are located beside estuaries and these ecosystems have served us well in terms of transport, trade and the provision of food. Estuaries also represent some of our most iconic tourist destinations. The wide range of human uses of estuaries, together with the number of people living beside them, means that inevitably not all activities can be supported everywhere. This dilemma is a major environmental challenge for New Zealand and most other countries with coastlines. This enhances the need to understand the ecosystem processes and the threats to them. Estuaries represent important meeting places between the land and sea and consequently are subjected to multiple and cumulative stressors. Despite the long list of potential stressors and the need for restoration in some locations, our estuarine and coastal ecosystems still exhibit high biodiversity values and are critical to our tourism industry and our sense of national identity.
Rivers, streams, drains and direct runoff from land bring a variety of contaminants to our estuaries and coasts. Modification of coastal and estuarine shorelines through reclamation, dredging and in-water structures (e.g., causeways, bridges, piers, marinas and structures associated with aquaculture) can also affect ecosystem process and as a result service delivery. While from the sea we bring stressors associated with fishing, mining and invasive species.
Estuaries, like coral reefs, are especially prone to the effects of climate change. Climate change in an estuarine setting can only be realistically viewed through a multiple stressor lens. With increased storminess and episodic rainfall we can expect changes in freshwater inputs and sediment runoff in many areas. In the estuary, temperatures and sea level are expected to rise, affecting habitats, species distributions and many of the processes that underpin provisioning ecosystem services. At the coast, changes in storminess, increased storm surge, changes in wave climate and changes in coastal productivity and coastal ocean currents are likely to affect estuarine ecology. Estuaries are also regions with high variation in water column pH, while this can be due to a number of natural factors it is exasperated by both local anthropogenic stress and global climate change. All of these stressors interact with other future cumulative effects on the ecosystem. For example, profound eutrophication effects such as decreasing the oxygen concentration in the floor of the estuary, creating dead zones, while primarily influenced by nutrient loading is also affected by temperature and salinity induced water stratification that may also change with change. Furthermore, the eutrophication status of estuaries can feed back on climate change through the production of greenhouse gases.
Capabilities Developed in this Course
|Capability 1:||Disciplinary Knowledge and Practice|
|Capability 2:||Critical Thinking|
|Capability 3:||Solution Seeking|
|Capability 4:||Communication and Engagement|
|Capability 5:||Independence and Integrity|
|Capability 6:||Social and Environmental Responsibilities|
- Analyse and interpret field data using appropriate methods (Capability 1, 2, 3, 4, 5 and 6)
- Evaluate relevant scientific literature (Capability 1, 2, 3, 4, 5 and 6)
- Explain complexity and functioning of soft sediment ecosystems, how science is conducted in these systems, the science behind management/conservation, and possible solutions to challenges caused by human activities (Capability 1, 2, 3, 4, 5 and 6)
- Demonstrate advanced communication of scientific information (Capability 1, 2, 4, 5 and 6)
- Critically interrogate environmental science in the media (Capability 2, 4, 5 and 6)
|Assessment Type||Learning Outcome Addressed|
a. Basic introduction to biogeochemistry, primary production and macrofauna
b. Trophic interactions
c. Biodiversity, feedback loops & resilience
a. Stressors, disturbance & recovery from catastrophic events: Sedimentation as a case study
b. Ecosystem based management
3. Conducting science in estuaries
a. Monitoring for change
b. Experimental field ecology
For this course (150 hrs), you can expect 20 hours of reading ahead of the field trip and 10 hours of preparing a short presentation (10 min) on science in the media. The week at LML (60 hrs) will be intensive involving seminars, discussions, designing and doing field work and data analysis. After the course you will submit an essay (20 hours) and a field trip report (40 hrs).
Attendance is required at LML for the week, the rest of the course can be done from where ever suits you.
a. First look at the seminar outlines and complete the required reading thinking about the questions posed. This is an exercise in learning about a new topic where you need to read scientific papers to acquire knowledge and come up to speed on concepts that maybe unfamiliar to you (i.e. research). Do not worry if you do not understand everything, we do not expect you to and there is no exam in this course! Think about some questions you would like answers to. Also think about selecting an essay topic then delve deeper into the literature.
b. Interactive discussion during seminars and other presentations is an opportunity to ask any questions and reinforce the key concepts. It is also an opportunity to ask questions related to your chosen essay topic. We expect students enrolled in the course will participate and contribute to these discussions – it is the primary way in which you will be able to engage with us directly and improve your grasp of the material.
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Elements of this outline may be subject to change. The latest information about the course will be available for enrolled students in Canvas.
In this course you may be asked to submit your coursework assessments digitally. The University reserves the right to conduct scheduled tests and examinations for this course online or through the use of computers or other electronic devices. Where tests or examinations are conducted online remote invigilation arrangements may be used. The final decision on the completion mode for a test or examination, and remote invigilation arrangements where applicable, will be advised to students at least 10 days prior to the scheduled date of the assessment, or in the case of an examination when the examination timetable is published.