Temperature

• Units: degrees Celcius or Fahrenheit
• Instrument Range: -5 to 35 deg C (accuracy of +/- 0.005 deg C)
• Description: Used here to denote the sea water temperature determined using the ITS-90 algorithm.

Tide

• Units: feet above mean lower low tide [datum] (converted from db; a pressure change of 1 decibar equals about 1 meter of seawater)
• Instrument Range: 0 to 20 m (accuracy of +/- 0.02 m)
• Description: This is measured by a strain gauge sensor. The mounted pressure sensor records the distance between the sensor and the surface of the water in decibars. The sensor is mounted below of (nominally 2 m below mean lower low water), but near the surface of the ocean.
• Notes: This is not an official tide guage, only an estimate of tidal action.

Salinity

• Units: Practical Salinity Units
• Instrument Range: 31.5 to 37 PSU
• Description: We can not directly measure this quantity, so it is calculated from the conductivity measurement using the UNESCO (1981) algorithm. Salinity quantifies the total amount of dissolved solids in seawater, so a salinity of 33 means that each kilogram of seawater contains 33 grams of total dissolved solids, mostly sodium chloride.
• Notes: It's possible that after some rain (which is not too common here), you can see the fluorometer values go up (as there is a new supply of nutrients for the oceanic plants), the percent transmission go down (due to the silty runoff), and even the salinity can go down (because the sensor is near the surface, and the new fresh water is near the surface too since it's less dense).

Bioluminescence

• Units: Volts
• Instrument Range: 0 to 5 Volts
• Description: A bathyphotometer measures the amount of bioluminescence (emission of light by some living organisms) in the water. At night at certain times of the year, you may see a form of bioluminescence as a faint blue-green light in breaking waves, wakes of boats, or even in your footprints on the beach.

Fluorometer

• Units: Volts
• Instrument Range: 0 to 5 Volts
• Description: This value is volts from the Fluorometer. It measures chlorophyll fluorescence by emitting an excitation beam at a known wavelength which causes chlorophyll to emit at a different, but known wavelength. This is a type of measurment of the amount of phytoplankton (unicellular plants in the water). If water appears more green than blue, their chlorophyll is probably the reason.

Transmissometer

• Units: Percent transmittance
• Instrument Range: 0 to 100 percent
• Description: Transmissometers measure the percent of light which is not attenuated (a decrease in light intensity in the water column due to absorption [by water molecules] and scattering [by suspended particulates]) within a given pathlength (in this case 0.25 m). You can think of this as a measurement of the clarity of the water (the higher the more clear).
• Notes: You may see the the transmittance slowly drop over a few weeks and then shoot up again. This is due to the essentially unavoidable phenomenon of bio-fouling (where stuff grows on our sensors), and after servicing it (about every other month) the signal will then appear closer to its actual value.
• As of Sep, 2007, this instrument has been discontinued.