Final answer:
The introduction of water hyacinth to a lake ecosystem is likely to cause a decrease in the number of types of plant species due to its tendency to form dense mats, block sunlight, and deplete oxygen levels, leading to a decline in native plants and animals. The correct option is option B.
Step-by-step explanation:
When water hyacinth, an invasive species, is introduced into a lake ecosystem where it was not previously located, it is most likely to have negative impacts on the native plant and animal species. Water hyacinth tends to form dense mats that cover the water surface, which blocks sunlight and reduces the oxygen levels in the water. This can lead to the decline of native aquatic plants that need light to photosynthesize and can create hypoxic conditions that are detrimental to aquatic animals. Over time, the number of types of plant species in the lake will decrease due to the competitive exclusion and habitat alteration caused by the water hyacinth.
Furthermore, the introduction of water hyacinth often leads to cultural eutrophication, where excessive nutrients, such as nitrogen and phosphorus from runoff, can cause explosive growth of the invasive plant, exacerbating the problem. These conditions create an unfavorable environment for native flora and fauna, thereby reducing biodiversity and disrupting the existing ecosystem balance.
Therefore, the correct option in the final answer to the question of how the introduction of water hyacinth will impact the ecosystem over time is (B) The number of types of plant species in the lake will decrease.