The paper discusses the preservation of elemental and isotopic source identification of sedimentary organic matter in lakes and oceans. Despite the significant degradation and alteration of organic matter during sinking and sedimentation, the C/N ratio and δ13C values of total organic matter retain paleoenvironmental information for multi-million-year time periods. The C/N ratio and δ13C values are useful identifiers of organic matter sources, distinguishing between algal and land-plant origins. The C/N ratio of algae is typically between 4 and 10, while vascular plants have ratios of ≥20. δ13C values reflect the biochemical pathways used by plants, with marine algae having a δ13C value of ~0‰ and C3 land plants having a shift of ~−20‰. δ13C values of C4 plants are ~−7‰. These identifiers help in tracing the sources and distribution of organic matter in coastal ocean sediments. The paper also reviews sedimentary records from various lakes and marine sites, including Mangrove Lake (Bermuda), Lake Baikal (Siberia), Lake Bosumtwi (Ghana), Lake Biwa (Japan), DSDP Site 619 (northern Gulf of Mexico), DSDP Site 532 (Walvis Ridge, South Atlantic), ODP Site 689 (Maude Rise, South Atlantic), ODP Site 805 (Ontong Java Plateau, north Pacific), and DSDP Site 443 (north Philippine Sea). These records show changes in organic matter sources over time, influenced by factors such as climate, sea level, and upwelling systems. The C/N and δ13C values in these sediments provide valuable information about past environments and help in understanding the reliability of bulk organic matter parameters as source indicators. The author concludes that while selective degradation and diagenetic modifications occur, the C/N and δ13C values of total organic matter retain source signatures for long periods, making them useful tools for paleoenvironmental and paleoclimatological studies.The paper discusses the preservation of elemental and isotopic source identification of sedimentary organic matter in lakes and oceans. Despite the significant degradation and alteration of organic matter during sinking and sedimentation, the C/N ratio and δ13C values of total organic matter retain paleoenvironmental information for multi-million-year time periods. The C/N ratio and δ13C values are useful identifiers of organic matter sources, distinguishing between algal and land-plant origins. The C/N ratio of algae is typically between 4 and 10, while vascular plants have ratios of ≥20. δ13C values reflect the biochemical pathways used by plants, with marine algae having a δ13C value of ~0‰ and C3 land plants having a shift of ~−20‰. δ13C values of C4 plants are ~−7‰. These identifiers help in tracing the sources and distribution of organic matter in coastal ocean sediments. The paper also reviews sedimentary records from various lakes and marine sites, including Mangrove Lake (Bermuda), Lake Baikal (Siberia), Lake Bosumtwi (Ghana), Lake Biwa (Japan), DSDP Site 619 (northern Gulf of Mexico), DSDP Site 532 (Walvis Ridge, South Atlantic), ODP Site 689 (Maude Rise, South Atlantic), ODP Site 805 (Ontong Java Plateau, north Pacific), and DSDP Site 443 (north Philippine Sea). These records show changes in organic matter sources over time, influenced by factors such as climate, sea level, and upwelling systems. The C/N and δ13C values in these sediments provide valuable information about past environments and help in understanding the reliability of bulk organic matter parameters as source indicators. The author concludes that while selective degradation and diagenetic modifications occur, the C/N and δ13C values of total organic matter retain source signatures for long periods, making them useful tools for paleoenvironmental and paleoclimatological studies.