Transitional words, phrases, and sentences — SHSAT practice questions

Small Islands at Work

(1) In many neighborhood ponds, rainwater carries soil, fertilizer, and decaying leaves from nearby pavement and lawns into the water. (2) These materials may remain suspended, making the water cloudy for weeks after a storm, or dissolve into compounds that alter the pond’s chemical balance. (3) One way to address the problem without rebuilding the banks is to install a floating wetland raft near the center of the pond. (4) Unlike a wetland planted along the shore, a raft supports plants on a buoyant platform with roots dangling in the water. (5) Pond water enriched with nitrogen and phosphorus can support unusually rapid algae growth during warm weather, even when the surface seems calm.

(6) Algae form dense surface mats that block sunlight from reaching submerged vegetation. (7) When algae die, bacteria decompose them, a process that consumes oxygen needed by fish and aquatic insects. (8) This cloudy water is very hard on fish and other pond life. (9) A small raft is assembled on land in a series of stages before entering the pond.

(10) First, volunteers fasten buoyant strips around a shallow tray to form a stable frame that will not tip easily. (11) Next, they pack the tray with coconut fiber or another porous material that retains moisture but allows roots to pass through. (12) Workers then fit sedge seedlings into openings in the fiber so the leafy crowns remain above it. (13) At the same time, the raft is lowered into the pond and towed to a sunny location away from boat traffic. (14) Finally, ropes connected to weighted anchors keep the island from drifting against the shore or blocking open water. (15) Once in place, the raft creates a boundary where pond water continuously moves past living roots and air reaches the plant stems.

(16) Colonies of microorganisms gather on the submerged root surfaces and break down some pollutants. (17) The roots absorb dissolved nitrogen and phosphorus that would otherwise feed algae. (18) Similarly, with fewer nutrients available, excessive algae growth becomes less likely, allowing more light to reach underwater plants. (19) The dense curtain of roots also creates shaded spaces beneath the raft. (20) Dragonfly young cling to the roots, while small fish search among them for food. (21) To evaluate the project, student monitors can measure water clarity, record temperatures at marked locations, and count aquatic insects each month.

(22) Comparing their findings with those from a similar pond without a raft cannot create a perfectly controlled experiment, but it can reveal patterns worth studying. (23) Floating wetland rafts are one of several structures that can be placed in a pond.