## 5 Hot Spring Activity
### Historic Accounts  
The hot springs of Saba, which were first described in 1903 [42], are all located close to the shoreline and orientated along a NE-SW line crossing the island. Over time, four different hot spring locations have been reported: (i) Well Bay; (ii) between Ladder and Tent Bay; (iii) submarine; and (iv) opposite Green Island (Figure 2). According to [PERSON] et al. [43] and [PERSON] and [PERSON] [2], the hot spring at Well Bay (i) was reported by [PERSON] [42] and was destroyed at some point thereafter. However, in the account of his visit to the islands, [PERSON] [42] reports the temperature of the hot spring (Table 3) between Ladder and Tent Bay (ii) and mentions another hot spring \"at the north side of the island\". He never states this hot spring to be located at Well Bay, and therefore, we regard the existence of this spring as unproven. The temperature of the hot spring between Ladder and Tent Bay (ii) has been measured at irregular intervals since [PERSON]'s first visit in 1903. Until 1994, the average measured temperature was around \(55\pm 4\)\({}^{\circ}\)C. Values measured after 1996 showed an increased average temperature of \(63\pm 3\)\({}^{\circ}\)C. In 1999, the temperature was measured for the last time, and the site was covered by a landslide, preventing any further measurements. A submarine hot spring (iii) 150 m offshore of Ladder Bay was discovered by SCUBA divers around 1988. A second submarine hot spring was reported in 1994, south of Green Island. No temperature measurements exist for these sites. The hot spring opposite Green Island (iv) on the shoreline at the north side of the island is located below the sulfur mine. Access to the site is complicated by the high surf and vertical cliffs. Between 1979 and 1994, temperatures of \(69\pm 3\)\({}^{\circ}\)C were measured. Between 1996 and 2008 temperatures of \(82\pm 4\)\({}^{\circ}\)C were measured, an increase comparable to the increase at the hot spring between Ladder and Tent Bay (ii). When we visited this site in January 2018, the spring was submerged below 30 cm of seawater, and our temperature measurement of \(69\)\({}^{\circ}\)C is, therefore, a minimum. \begin{table}
\begin{tabular}{c c c c} \hline
**Date Measured** & **(ii) Ladder Bay (\({}^{\circ}\)C)** & **(iv) Green Island (\({}^{\circ}\)C)** & **(v) Sulfur Mine (\({}^{\circ}\)C)** & **Measured and Reported by** \\ \hline
1903 & 542 & & & [PERSON] (1903) \\
15 March 1950 & 55–57 & & Western and Kiel (1961) \\
22 July 1979 & & & 31.5 & [PERSON] and [PERSON] (2004) \\
25 July 1979 & 51 & & & [PERSON] and [PERSON] (2004) \\
27 July 1979 & 55 & 72 & [PERSON] and [PERSON] (2004) \\
26 August 1981 & 55 & 66.5 & [PERSON] (in R and 5 2004) \\
9 March 1994 & & 54 \({}^{\ast}\) & 32.5 & [PERSON] and [PERSON] (2004) \\
10 March 1994 & 54.2 & & [PERSON] and [PERSON] (2004) \\
13 April 1996 & & 80 & [PERSON] (in R and S, 2004) \\
24 September 1996 & & 82 & [PERSON] (in R and S, 2004) \\
30 January 1997 & 62 & & [PERSON] and [PERSON] (2004) \\
27 August 1997 & 62 & [PERSON] (in R and S, 2004) \\
17 March 1998 & 64 & & [PERSON], [PERSON] (from SCF) (2004) \\
9 April 1998 & & 79 & [PERSON] (in R and S, 2004) \\
5 May 1998 & 61 & & [PERSON] (from SCF) \\
6 May 1998 & & 84.7 & [PERSON] (from SCF) \\
30 May 1999 & 66 & 88 & [PERSON] and [PERSON] (from SCF) \\
28 May 2005 & & 84 & 36 & [PERSON] (from SCF) \\
7 August 2005 & & 84 & 34 & [PERSON] (from SCF) \\
15 October 2007 & & 86 & 47 & [PERSON] and [PERSON] (from SCF) \\
28 October 2008 & & 86 & 45 & [PERSON] (from SCF) \\
31 January 2018 & & 69 \({}^{\ast}\) & & This work (2018) \\ \hline \end{tabular}
\end{table} 
Table 3: Temperatures measured at the hot spring between Ladder and Tent Bay, the the hot spring opposite Green Island and inside the Sulfur Mine. \({}^{\ast}\) denotes the minimum temperature due to submersion of the spring. More recent numbers collected by the Saba Conservation Foundation (SCF).