Deep in Mud: Benthic Foraminifera Interface Marine Sediment-Water—Sampling, Handling, and Analyzing

Sampling shallow or deep environments requires different techniques due to particular and irregular morphology in the marine sediments worldwide. Independent of the way sampling is performed, systematic methodology for handling and analyzing are similar. Measurements of surface and bottom water properties, generally done at the time of collection, help us identify bottom water mass and its link to specific living benthic assemblages. When analyzing marine sediment samples, a qualitative approach where main indicator species are selected is based on the relationships between their specific distribution patterns and the bottom hydrographic data (salinity, temperature, dissolved oxygen, suspended matter, pH, silica, nitrite, and nitrate), and geological data (grain sizes, carbonates, and organic matter) and other available parameters are a good choice when detecting patterns. Dead shells are observed in relation to the state of test conservation due to acidity and transportation, and occurrence and extinction of specific species delimits stages, epochs, and periods of time can be quite interesting. Quantitative analysis based on counts of living specimens can be descriptive or analytical in recent and in the past millions of years. Numbers of individuals are counted and the individual absolute and relative abundance (dead/unstained and alive/stained) are calculated. Maps of spatial distribution of relative abundance of species are important to illustrate and understand tendencies since each datum relates to its geographic coordinates. Univariate and multivariate analysis, ecological indexes like diversity, dominance, evenness, hypoxia (AE index), FORAM Index (FI), and the paleo temperature (“Warm” species index) are applied to foraminiferal and environmental data to further unravel particular situations, and are effective to assess changes in community structure helping us to find the problem and propose a better solution for the best quality of marine sediment through maps. Mapping the placement of samples reflects the similarity of their biological communities, environmental patterns, and indicators of biodiversity and stability, rather than their simple geographical location. Recently the association between ‘warm’ species index, organic carbon flux, and modern bottom water temperatures has started to show excellent results on depth and differentiation of relatively warm groups (>3.5 °C) with higher carbon flux (>3.5 g C m−2 year−1) versus a group that reflects the colder, deeper waters with lower carbon flux in a deep water section of the Western Pacific Warm Pool, the warmest area of the Pacific. Relatively high abundances of an indicator species (Uvigerina prosbocidae) of paleo productivity from organic matter input associated with down-slope movement in a tectonically unstable region shows co-variates with ‘warm’ species groups, providing evidence for the use of this species as a tracer for carbon flux. Marine stable isotopes (δ 18O and δ 13C) also can detect salinity and temperature patterns near freshwater sources or near the ocean. Historical changes in the mixing between fresh versus marine waters of bays and estuaries should follow spatial sense, and they can be determined by analyzing faunal sequences and geochemical signatures in cores of its substratum. By applying both qualitative and quantitative approach we have a better knowledge of the environment and the details are not lost.