LAGOS-US LIMNO: Data module of surface water chemistry from 1975-2021 for lakes in the conterminous U.S.

The LAGOS-US LIMNO data package is one of the core data modules of LAGOS-US, an
extensible research-ready platform designed to study the 479,950 lakes and reservoirs larger
than or equal to 1 ha in the conterminous US (48 states plus the District of Columbia). The
LIMNO module contains in situ observations of 47 parameters of lake physics, chemistry, and
biology (hereafter referred to as chemistry) from lake surface samples (defined as
observations taken from the epilimnion of a lake) obtained from the Water Quality Portal,
the National Lakes Assessment (2007, 2012, 2017), and NEON programs. LIMNO provides
3,511,020 observations across all parameters collected between 1975 and 2021 from 20,329
lakes; the number of observations per lake ranged from 1 to 20,605 with a median of 32. The
database design that supports the LAGOS-US research platform was created based on several
important design features: lakes are the fundamental unit of consideration, all lakes in the
spatial extent above the minimum size must be represented, and most information is connected
to individual lakes. The design is modular, interoperable (the modules can be used with each
other, as well as other comprehensive lake data products such as the USGS NHD), and
extensible (future database modules can be developed and used in the LAGOS-US research
platform by others). Users are encouraged to use the other two core data modules that are
part of the LAGOS-US platform: LOCUS (location, identifiers, and physical characteristics of
lakes and their watersheds) and GEO (characteristics defining geospatial and temporal
ecological setting quantified at multiple spatial divisions) that are each found in their
own data packages.