Since the 1970's, when the first in situ measurements of oxygen in the ocea
ns were reported the development of electrochemical sensors for in situ mea
surements in aquatic systems has significantly intensified. A synthesis of
the progress made in limnology and oceanography to measure chemical species
in situ is presented. From amperometric and potentiometric sensors that ca
n measure a single analyte to voltammetric sensors that can measure several
species during the same scan, a variety of electrodes have been used in si
tu to better understand the nature of the biogeochemical processes occurrin
g in aquatic systems. The advantages and disadvantages of each technique, t
he technical improvements over the years, and some recommendations are pres
ented together with representative data reported in the literature over the
last two decades.