Fig 1.
Map of the Narrow River, also called the Pettaquamscutt River, and Point Judith Pond estuary.
The four locations sampled by [13] and revisited in 2010–2012 are indicated by closed circles and labeled as Bridgetown, Middle Bridge, Harbor Island, and Galilee. The open circles indicate the location of the deeper water temperature measurements made by [23] and [24]. The location of NOAA’s Newport, RI temperature monitoring station is also noted in the inset map.
Table 1.
Data sources and additional details on temperature data used in Figs 2–6.
Bridgetown is Station I, Middle Bridge is Station II, Harbor Island is Station III, and Galilee is Station IV. Data locations are shown in a regional context in Fig 1.
Fig 2.
Monthly temperature data for the Narrow River.
The top panel (A) presents available monthly temperature data from the shallow intertidal portion of the Upper Narrow River estuary at the Bridgetown Station. The bottom panel (B) presents available data from the Middle Bridge Station. In both panels, black bars represent temperature measured by [13] and gray bars represent temperature measured as a part of this study. Shapes represent data taken from the literature. Bars over data points represent standard deviation. Data sources are listed, and described in more detail, in Table 1.
Fig 3.
Monthly temperature data for the Harbor Island (upper estuary, A) and Galilee (lower estuary, B) stations in the Point Judith Salt Pond.
Black bars represent mean monthly water temperatures measured by [13] and gray bars represent data collected as part of this study. Bars over data points represent standard deviation. Shapes represent data taken from the literature and published reports. For detail on data sources, see Table 1.
Fig 4.
Differences in mean monthly temperatures measured in 2010–2012 (as part of this study) and the earliest full year of available data for our four study locations.
The Bridgetown and Middle Bridge (Narrow River) data points represent the difference between the temperature data from this study and measurements made between April 1972-May 1973 [19]. The Harbor Island and Galilee (Point Judith Pond) data points are the difference between this study and data from July 1967-June 1968 [21]. Data from the shallow water stations are shown as open and shaded circles. For reference, we included data from NOAA’s Newport, RI temperature monitoring station [11,25]. The difference between mean monthly temperature measurements in Newport from the time period of this study and both the April 1972-May 1973 and July 1967-June 1968 time periods are shown as closed and open squares. Positive values indicate an increase in temperature over time and negative values indicate cooler temperatures today. The mean of all of the monthly temperature anomalies for all of the shallow water stations, was approximately 3.9°C. If the 2012 data are omitted from the dataset, this value drops to 3.5°C.
Fig 5.
Annual temperature anomalies at Newport, RI (41° 30.3’ N, 71° 19.6’ W).
Mean annual temperature data from 1955–2012 were averaged, with the exceptions of 1995, 1996, and 2002 when full years of data were not available (and not shown) [25]. Annual deviations from this average are shown as bars. Positive values indicate mean annual temperatures that are warmer than the long-term average and negative values indicate colder than average annual temperatures. Solid black bars at 1967–1968 and at 1972–1973 are used to indicate the earliest annual data available for Point Judith Pond and Narrow River, respectively, as described in Fig 4. The bar for 1973 is not visible as the annual temperature for that year was so close to the long term average (11.7°C). The years where temperature data were collected as a part of this study (2010–2012) are also indicated by solid bars.
Fig 6.
Individual monthly temperature measurements from this study plotted against monthly temperature measurements from nearby deeper waters, collected during the same time period (June 2010-May 2012) [23,24].
Monthly deeper water temperature measurements were available from May to October for each year. The bold black line is the 1:1 line, while the subsequent dashed and thinner solid lines reference the 5°C and then 10°C warmer above the 1:1 line and are included only for reference. Deeper water sample stations are shown in Fig 1.
Fig 7.
Total catch data from [13] and this study for the Narrow River (Bridgetown + Middle Bridge, top panel) and Point Judith Pond (Harbor Island + Galilee, bottom panel).
Mulkana’s data [13] are plotted as closed circles and our data are plotted as open circles (2010–2011) and gray circles (2011–2012). Total catch is the sum of all individual fish captured in each estuary on a given sampling trip. Note the different scales on the Y-axis between the top and bottom panels. As Mulkana began his study in July 1962, the X-axis begins in July and ends in June.
Fig 8.
Approximate temperature increases since 1965 are shown for air, the open ocean, Northeastern United States estuaries, and our observations from the shallow intertidal portion of the estuaries.
The size of the circle gives a rough approximation of the variability surrounding these measurements. Our observations are denoted with a dashed line as they are less certain. For example, air temperatures have increased by 0.13°C (range 0.10–0.16°C) per decade between 1956 and 2005, or about 0.6°C (range 0.5–0.8°C) since 1965 [1]. Similarly, our estimate of open ocean temperature increase comes from [2] (0.3°C between 1948–1998) in the surface 300 m of the ocean as well as from [56] who showed an approximate rise in sea surface temperature of about 0.4°C since the 1960s. Water temperature data for the Northeast estuaries comes from [5,6], where they observed a temperature increase of ~1.4°C from the 1960’s and 1990’s in Woods Hole, Massachusetts. Data from Boston Harbor, Massachusetts and Newport, Rhode Island are consistent with this trend [6]. The mean annual increase in temperature at our four stations (i.e., Northeast U.S. intertidal) ranged from 3.3–4.7°C, with an average of 3.9°C. If the 2012 data are omitted, this range shifts to 2.5–4.5°C with an average of 3.5°C. The dashed gray circle represents the range of values including 2012.