Final answer:
Spring tides push wrack closer to dune vegetation, releasing nutrients as it decomposes, thus enhancing the growth and health of the dune ecosystem.
Step-by-step explanation:
Spring tides, which occur when the sun and moon are in alignment with the earth, lead to higher than average high tides and lower than average low tides. This increased tidal movement can enhance the delivery of nutrients from the wrack line to the dune vegetation. Wrack, which consists of organic material such as seaweed and seagrass, is often deposited at high tide lines on beaches.
During spring tides, the higher high tides can push this material further onto the shore, closer to the dunes. As this organic matter decomposes, it releases nutrients into the soil, which can be taken up by the vegetation. Dune plants benefit from these nutrients, leading to healthier ecosystems and bolstering the dune's role as a natural coastal defense against erosion.