Anthropogenic Modifications to Estuaries Facilitate the Invasion of Non-Native Species
Round 1
Reviewer 1 Report
The manuscript titled: “Anthropogenic modifications to estuaries facilitate the invasion of non-native species” is a review of the issues surrounding the transportation and suitability of invasive species in harbor and estuary environments. This manuscript is interesting and well written. Much of it focuses on the transportation of propagules through the ballast water of ships and the lack of regulation or mechanisms involved in preventing unintended transportation. The manuscript also does a great job in describing how these invasive non-natives are often better suited to be able to survive in the environments in which they are introduced. My one question as a reviewer was that if ship ballast water, the encrusting and subsequent hitchhiking of adults on ships, and addition of aquaculture and coastal structures providing new attachment substrates are all mechanisms which will promote the transportation of non-native species, wouldn’t we expect invasions to have been occurring for 100s of years? Is it possible to tease apart the invasion of species from 100 years ago and 10 years ago? Perhaps adding a section early in the manuscript discussing the influences of wooden ships, antifouling chemicals like copper which used to be used on ships, and then modern treatments of ballast water, their failings, and what can be done would provide a bit more context and relevance for this manuscript.
Author Response
Ref: processes-1178236
Title: Anthropogenic modifications to estuaries facilitate the invasion of non-native species”
Response to reviewer 1:
Thank you very much for your comments. We have answered your points below.
The manuscript titled: “Anthropogenic modifications to estuaries facilitate the invasion of non-native species” is a review of the issues surrounding the transportation and suitability of invasive species in harbor and estuary environments. This manuscript is interesting and well written. Much of it focuses on the transportation of propagules through the ballast water of ships and the lack of regulation or mechanisms involved in preventing unintended transportation. The manuscript also does a great job in describing how these invasive non-natives are often better suited to be able to survive in the environments in which they are introduced. My one question as a reviewer was that if ship ballast water, the encrusting and subsequent hitchhiking of adults on ships, and addition of aquaculture and coastal structures providing new attachment substrates are all mechanisms which will promote the transportation of non-native species, wouldn’t we expect invasions to have been occurring for 100s of years? Is it possible to tease apart the invasion of species from 100 years ago and 10 years ago? Perhaps adding a section early in the manuscript discussing the influences of wooden ships, antifouling chemicals like copper which used to be used on ships, and then modern treatments of ballast water, their failings, and what can be done would provide a bit more context and relevance for this manuscript.
Response: According to the suggestions, we added into the introduction (page 1-2, Line 40-58) the next consideration:
The extensive and accidental introduction of organisms in waters is a direct consequence of the intensity with which humans utilize this via for worldwide commerce [3]. Alt-hough, it is not possible to tease apart the invasion of species from 40 years ago due to the lack of records and long-term series, it is likely that the GoC present continues pressure at least since 1492, when Columbus sailed between this gulf and The Americas by wood-en-hulled ships. From the 1500s, wooden-hulled ships could be colonized by marine or-ganisms which have been carried to many parts of the world, resulting in broad geo-graphic distributions [4, 5]. The use of steel as the primary ship-building material in ves-sels forced to use anti-fouling paints which resulted in significant impacts to marine communities such as TBT or tri-butyl tin [6]. However, other constituents of antifouling paints to prevent the spread of species on vessel and boat hulls such as copper and zinc which are common seems to confer a competitive advantage on some non-indigenous marine invertebrates [7]. For instance, invasive bryozoans display a high tolerance to the toxic heavy metal copper [8] being a mechanism for the selection of toxicant tolerance in non-native species (see section 3). Finally, although it is likely that the main transport of species could be associated to merchant vessels, we should take into account the situation for non-merchant vessels. For instance, recreational vessels are commonly transported to new locations by water without any attempt at cleaning.
In regards to modern treatments of ballast water, in the text and conclusions we mentioned some paragraphs:
“However, due to advances in new techniques for species detection, the detection of many microscopic organisms is increasing, also including the early stages of the development of macroscopic organisms. In this scenario, a high abundance of microorganisms (including those below 10 μm in size) has been demonstrated in ballast waters and may have a significant impact on the receiving environment. Consequently, this fact should, perhaps, be taken into account in the discharge standards [9]”
“In order to overcome these challenging conditions properly, the assessment and validation of ballast water treatment systems that can efficiently overcome these two factors (biotic and abiotic) is encouraged. This, should involve a “worst case scenario” that could actually occur in real water conditions [18,73]. Additionally, the development of efficient ballast water management systems in these scenarios would also benefit some related industries, such as aquaculture, which is also, potentially, affected by possible spread of organisms resulting from an inadequate ballast water management [61,70].”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This study is important for offering an understanding of how the anthropogenic modifications of estuaries facilitate the invasion of non-native species.
The literature review is well written.
In my opinion, the scope of the paper and the limitations need to be better emphasized together with the research methodology. These will clarify the relevance of the work and of the conclusions.
Regarding the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWMC), please note that it came into force in 2017. Recommendation: update the line 37, reference here: https://www.imo.org/en/MediaCentre/HotTopics/Pages/Implementing-the-BWM-Convention.aspx
Author Response
Ref: processes-1178236
Title: Anthropogenic modifications to estuaries facilitate the invasion of non-native species”
Response to reviewer 2:
Thank you very much for your comments. We have answered your points below.
This study is important for offering an understanding of how the anthropogenic modifications of estuaries facilitate the invasion of non-native species.
The literature review is well written.
In my opinion, the scope of the paper and the limitations need to be better emphasized together with the research methodology. These will clarify the relevance of the work and of the conclusions.
Response: We have added a paragraph clarifying the context of this short communication – essay. Page 1, Line 31-40:
The overall number of published articles about biological invasions appears, however, to be significantly biased towards new records, the hypothesis of the entrance of NIS in the recipient environment or the potential impacts in the native biological community; few studies analyzed the activities which they could determine species traits that affect the success of NIS post-arrival [2].
This communication is more an essay to reinforce the hypothesis that anthropogenic modifications (such as chemical alterations and modified environments) benefit NIS with broad environmental tolerances and how these invasive non-natives are often better suited to be able to survive in modified estuaries in which they are introduced.
Regarding the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWMC), please note that it came into force in 2017. Recommendation: update the line 37, reference here: https://www.imo.org/en/MediaCentre/HotTopics/Pages/Implementing-the-BWM-Convention.aspx
Response: Corrected in page 2, line 64. Reviewer is right, although the IMO-BWMC convention was adopted in 2004, it was ratified by >75% of the global fleet by tonnage in 2016, so the entry into force was by September 2017. Thanks for the observation.
https://wwwcdn.imo.org/localresources/en/About/Conventions/StatusOfConventions/StatusOfTreaties.pdf
