Intertidal soft-sediment community does not respond to disturbance as postulated by the intermediate disturbance hypothesis

Survey of intertidal ecosystem reveals a legacy of potentially toxic elements from industrial activity in the Skeena Estuary, British Columbia, Canada

“…Persistent localised biological signals of historic disturbances in mudflats that are currently relatively undisturbed have been observed before on the north coast of BC [27]. To the best of our knowledge, no current disturbances are occurring in the Skeena estuary that can explain the small-scale indicators of disturbance observed in the biological community [10, 15, 22, 27]. Therefore, we hypothesise that fine-grained biological indicators of disturbance in the Skeena estuary are a legacy of past disturbances [10, 15].…”

“…Findings of previous surveys of the benthic invertebrates inhabiting the intertidal sediment in the Skeena estuary reveal an infaunal community that is relatively undisturbed at the estuary scale, but which still shows the scars of historic disturbance at finer-grained scales [10, 15, 21, 22]. Amphipods are powerful indicator species [23–27] whose high densities throughout the Skeena estuary [10, 15] suggests that current disturbances to intertidal areas are relatively limited. Similarly, we observe 40 intertidal species in this area, including multiple species at all trophic levels within the foodweb [10, 15], and such a complex community is often associated with non-disturbed habitats [4, 28–30].…”

“…Amphipods are powerful indicator species [23–27] whose high densities throughout the Skeena estuary [10, 15] suggests that current disturbances to intertidal areas are relatively limited. Similarly, we observe 40 intertidal species in this area, including multiple species at all trophic levels within the foodweb [10, 15], and such a complex community is often associated with non-disturbed habitats [4, 28–30]. Conversely, disturbed sites are often more easily invaded by invasive species [31, 32], and Capitellidae (Capitella capitate species complex) polychaetas are often observed in disturbed habitats, particularly areas that have been organically enriched [4, 27, 28, 33].…”

“…Conversely, disturbed sites are often more easily invaded by invasive species [31, 32], and Capitellidae (Capitella capitate species complex) polychaetas are often observed in disturbed habitats, particularly areas that have been organically enriched [4, 27, 28, 33]. Capitellidae polychaetas have a clumped distribution within the Skeena estuary and can be locally abundant at the scale of a 1m 2 plot [10, 15]. Similarly, abundant but localized populations of the invasive Cumacea Nippoleucon hinumensis , have been observed in the Skeena estuary [10, 15], and on other historically impacted mudflats along BC’s north coast [27].…”

“…Capitellidae polychaetas have a clumped distribution within the Skeena estuary and can be locally abundant at the scale of a 1m 2 plot [10, 15]. Similarly, abundant but localized populations of the invasive Cumacea Nippoleucon hinumensis , have been observed in the Skeena estuary [10, 15], and on other historically impacted mudflats along BC’s north coast [27]. While the universal presence and high abundances of amphipods, coupled with the complexity of the intertidal community at the estuary scale strongly suggest that these intertidal communities are relatively undisturbed, the locally abundant populations of invasive species and Capitellidae polychaetas offer contradictory evidence.…”