We investigate whether sediment grain-size and foraminiferal data may be used to recognize hurricane activity in sandy barrier island sediments, specifically on Bear Island, North Carolina, USA. Eighteen locations were sampled in 2016 following a five-year quiescent interval. The same sites were resampled in 2018 following Hurricane Florence, and again in 2019 following Hurricane Dorian. Samples were used to test the hypothesis that different sediment sources and transport directions were activated by each storm, thus leading to varying foraminiferal assemblages, and changed sediment characteristics in barrier island environments. The effects of hurricanes Florence and Dorian on sediments and foraminifera of barrier island environments proved to be different and complex. Hurricane Florence reduced environmental distinction and Hurricane Dorian had a lesser effect likely due to its lower energy and different track. Thus, the contrasting energy of these hurricanes, their tracks, and wind directions, were important determinants of changes to the barrier islands that took place in 2018 and 2019. Each hurricane has its own characteristics and subsequent effects on barrier island sedimentological and micropaleontological characteristics. Recognition of discrete episodes of hurricane-driven onshore transport in the sand-rich part of the stratigraphic record of a barrier island system adjacent to a sediment-starved shelf is unlikely.

Studying symbiotic interactions provides valuable insights into the ecology of extinct organisms and the broader mechanisms of evolution. Here we describe the earliest symbiotic associations between colonial corals and gastropods from the Late Ordovician of Estonia. Tabulate corals of the genus Heliolites were found in association with gastropod Ruedemannia borkholmiensis, Pachystrophia sp., and Hormotoma scorbiculata. Heliolitids encrusted only mature gastropod specimens presumably due to the need for an ample space to grow. During the Katian and Hirnantian in Estonia, gastropods provided a hard substrate for corals in areas where the seafloor was otherwise soft. The corals can use their hosts to escape unfavorable environmental conditions and withstand burial. The calcareous layer deposited by the coral strengthened the gastropod shell, making it more resilient and resistant to breakage in the event of predation by durophagous organisms or hydrodynamic events. The occurrence of the same species of gastropods and heliolitids in the Pirgu and Porkuni regional stages, independently, suggests that the symbiotic relationship between them was facultative for both partners. Taking into account the potential benefits and drawbacks involved, mutualism appears to best describe the associations between heliolitids and gastropods in the Late Ordovician of Estonia. The analysis of studied specimens suggests that corals began to colonize gastropod shells as early as the late Katian, either alive or secondarily inhabited by other invertebrates. This indicates that the innovation of coral colonization of motile gastropod shells may have emerged after the Great Ordovician Biodiversification Event (GOBE) in Baltica.