Estimating propagule pressure and viability of diatoms detected in ballast tank sediments of ships arriving at Canadian ports

Abstract

This research uses the concept of propagule pressure (number of individuals introduced and number of introduction attempts) to investigate human-mediated bioinvasion patterns. We quantified diatoms in the sediments of ballast tanks of commercial ships arriving on both Canadian coasts during 2007 to 2009. Diatom cell concentrations varied from non-detected to 10 5 cells g -1 wet weight (10 11 cells per tank). Although the lowest values were often found in tanks that underwent ballast water exchange, the highest concentrations (10 9 to 10 11 cells per tank) were detected in all voyage categories: transoceanic with ballast exchange (TOE), and intra-coastal with exchange (ICE) and without exchange (ICU). For the west coast, 36% of tanks carried detectable quantities of diatoms and there was no statistical difference between ship categories. For the east coast, 60% of tanks contained diatoms; ICU represented a bioinvasion pattern based on more frequent events with consistently lower cell concentrations, whereas ICE and TOE corresponded to less frequent events, though more variable in cell concentrations. Diversity reached 40 taxa per tank, including resting stages and cells that were supposedly growing vegetatively. New records may lead to introduction hypotheses that ought not to be accepted uncritically. Cell viability was tested using the vital stain fluorescein diacetate; parallel counts of protoplasm integrity and chlorophyll autofluorescence revealed that all 3 indicators gave results within the same order of magnitude. Inoculation of 0.2 to 0.5 ml of the slurry into culture media led to the growth of diatoms, even of taxa not initially detected. Within 7 d, cultured assemblages reached cell concentrations equivalent to 1.8 to 4.4 doublings of the original inoculation. KEY WORDS: Diatoms · Biological invasion · Ballast sediment · Propagule pressure · Phytoplankton viability Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 425: [47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] 2011 A wide range of organisms are transported in ship ballast tanks (e.g. Medcof 1975, Carlton 1985, Carlton & Geller 1993, Galil & Hülsmann 1997, Drake et al. 2007 and, among the microalgae, diatoms and dinoflagellates are well represented in abundance and diversity (e.g. Hallegraeff & Bolch 1992, Marangoni et al. 2001, Forbes & Hallegraeff 2002, Burkholder et al. 2007, Klein et al. 2009a. Dinoflagellates have been a frequent target of more in-depth investigation (Hallegraeff & Bolch 1992, Rigby & Hallegraeff 1994, Hamer et al. 2000, 2001, Pertola et al. 2006. This is mostly due to a valid perception of the survival advantage of cyst-forming species under the adverse conditions found in ballast tanks, as well as being a repercussion of case studies of toxin-producing species known to impact fisheries and aquaculture, whose bioinvasion histories have been charted based on paleontological records and/or molecular evidence (McMinn et al. 1997, Scholin 1998, Doblin et al....

Cryptic diversity in a cosmopolitan diatom known as Asterionellopsis glacialis (Fragilariaceae): Implications for ecology, biogeography, and taxonomy

“…Twenty‐four monoclonal cultures of Asterionellopsis were established using the single‐colony isolation technique (Andersen, 2005) from seawater collected at locations listed in Table 1 and from sediments accumulated in ship ballast tanks (arriving from the port of Saint John's, Newfoundland, Canada, to the port of Halifax, Nova Scotia, Canada on 30 July 2009) collected as described by Villac and Kaczmarska (2011). These, together with clones isolated from surface water in Bedford Basin (near port of Halifax) are collectively labeled as East Coast (EC) clones.…”

Relationship between propagule pressure and colonization pressure in invasion ecology: a test with ships' ballast

“…Methods for sample collection, enumeration and identification may be found in the scientific literature [15,16,[23][24][25]34,35]. Port samples were collected and processed following the same methods as for ballast water.…”

“…(c) Statistical analysis Based on previous research, data for CP : PP relationship analyses were grouped into three categories: exchanged water samples, unexchanged water samples and sediment [15,[23][24][25]. Abundance and species richness data for each taxonomic group were log-transformed (log(x þ 1)) to meet assumptions of parametric tests, allowing for comparisons between taxa.…”

Modeling the relationship between propagule pressure and invasion risk to inform policy and management

“…Regardless, it is not clear that the risk and release variables are well matched in space, time, and taxonomic resolution. Even if they were, the use of vessel characteristics for propagule pressure would be premised on the critical assumption that organism density and diversity is homogeneous across tanks and vessels-an assumption that is well known not to hold (e.g., Smith et al 1999, Murphy et al 2002, Minton et al 2005, Lawrence and Cordell 2010, Sun et al 2010, Casas-Monroy et al 2011, Villac and Kaczmarska 2011. Thus, it is not clear a priori that either propagule pressure or colonization pressure should necessarily be expected to correlate strongly with currently available measures of vessel traffic.…”