D. Removal of large woody debris LWD reduces channel scour, reduces macroinvertebrate drift, supplies habitat, and traps sediment. Removal of the LWD would reduce habitat for fish and invertebrates, increase downward movement of sediment, increase channel scouring, etc. On a continuum from smaller to larger in terms of water quality decision making, woody debris piles, bridge construction, nutrient loading, and the spread of zebra mussels increase in spatial scale. A woody debris pile is at the smallest scale and classified as habitat. Bridge construction can be considered on a small watershed scale where water quality is affected by land use.
Nutrient loading is at the watershed scale.
If an area values economic growth, water quality may be sacrificed. Sara may be concerned how their actions will affect her parents' marina and may bias the group in a certain direction. Other values of the river could be native biota, water quality, aesthetics, economic value, natural system function, human health, and cultural and spiritual. Using the spread of the zebra mussel as an example, with the St. Croix River as the resource at risk, protecting biodiversity can provide the water quality goal. Scientists have determined that the St. Croix may be suitable habitat for a zebra mussel colony and needs management protection to prevent the spread of zebra mussels from the Mississippi River.