Tidal Stream Reaches Dominated by Small Streams and are Vulnerable to Sea-Level Rise
Abstract
Rivers and streams represent a small percentage of the Earth's surface area, but play a large role in global biogeochemical and ecological cycles. Terrestrial-aquatic interfaces (TAIs) of rivers and streams (i.e., tidal streams) are an important component of global carbon and nutrient budgets and TAIs within the tidal stream corridor are particularly relevant due to the potential for elevated biogeochemical cycling rates and greenhouse gas emissions that result from dynamic surface-groundwater exchange. However, our knowledge of how tidal streams influence material budgets and ecosystem services has major gaps due to the common perception that "coastal interfaces" are mostly associated with large river deltas, resulting in limited studies of small tidal systems. Focusing on the conterminous US, we provide a foundation for understanding the role of tidal streams. We find that 66% of tidal stream length is from low order streams, and that terrestrial ecosystem production in low-lying coastal zones is 30% greater than in adjacent terrestrial ecosystems. There is a relatively small difference in stream order length contributions between tidal and non-tidal systems, indicating that small coastal watersheds dominate tidally-influenced spatial domains. We find that relative sea-level rise will have a large impact on low order tidal streams and their terrestrial interfaces. Though upstream reaches of tidal zones will be extended in response to RSLR, the gains are expected to be much smaller than what is lost because topographic gradients become steeper moving inland. The tidal portion of future streams will therefore be compressed, leading to shorter tidal reaches and decreases in tidal TAI. These results highlight previously unrecognized dominance, high productivity, and disproportionate future loss of low-order coastal ecosystems. This indicates a critical need to focus study on small tidal stream systems under contemporary and future conditions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H52B..06T
- Keywords:
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- 1817 Extreme events;
- HYDROLOGY;
- 1830 Groundwater/surface water interaction;
- HYDROLOGY;
- 1890 Wetlands;
- HYDROLOGY;
- 4235 Estuarine processes;
- OCEANOGRAPHY: GENERAL