Underwater grasses in the Chesapeake Bay grew by 7% in 2025, according to researchers from William & Mary's Virginia Institute of Marine Science (VIMS) and Batten School. The annual aerial survey found a total of 89,385 acres (140 square miles) of submerged grasses in the Bay and its tidal rivers, an increase of nearly 6,100 acres from the previous year. This marks the highest recorded coverage since 2018 and brings the Bay closer to its 2030 goal of 90,000 acres (141 square miles) under the Chesapeake Bay Watershed Agreement. The current total represents about 45% of the long-term goal of 196,600 acres (307 square miles) set for the region. The growth was largely driven by increases in grasses in higher-salinity areas of the Bay. In the Polyhaline Zone, which includes the saltiest waters near the Bay’s mouth, grass coverage expanded from 25,266 acres (39 square miles) in 2024 to 28,142 acres (44 square miles) in 2025, setting a new record for the second year in a row. The Mesohaline Zone, which has moderately salty water, also saw a nearly 15% increase, growing from 33,033 acres (52 square miles) to 37,879 acres (59 square miles). Researchers credit this growth to improved water clarity in the lower Bay, a result of long-term water quality improvements. These changes have allowed eelgrass, a key species, to thrive and spread into deeper waters. However, not all parts of the Bay saw growth. The Tidal Fresh Zone, which includes rivers and bays near the headwaters, saw a decline, dropping from 20,221 acres (32 square miles) to 18,653 acres (29 square miles). This decrease was particularly noticeable in Virginia tributaries like the upper Rappahannock River. The loss was mainly due to reduced coverage of Hydrilla verticillata, an invasive aquatic plant that has fluctuated in different areas over recent years. The Oligohaline Zone, which has slightly salty water, remained relatively stable at just over 4,700 acres (7.3 square miles), as gains in some areas balanced out losses in others. Underwater grasses play a crucial role in the Bay’s ecosystem, providing habitat for fish, crabs, and waterfowl, while also improving water quality by absorbing nutrients, stabilizing sediments, and producing oxygen. Historical records suggest the Bay once supported between 200,000 and 600,000 acres (313 to 938 square miles) of these grasses, but by 1984, coverage had dropped to around 39,000 acres (61 square miles). Efforts to reduce nutrient pollution have helped double the grass coverage since then. While the 2025 survey shows continued progress, challenges like climate change, land-use changes, and localized environmental stressors remain. Researchers believe the recent improvements in grass coverage are a sign that these conservation efforts are still effective.