Alien invasion book where the aliens first introduce an invasive species from another planet to weaken them

Question

I'm trying to find a science fiction book from many years ago but I don't remember the name or author. I borrowed it from the library in the late '80s or early '90s.

The plot was generally about an alien race that invaded planets by first transplanting species from other planets that would destroy the inhabitants of the planet they were interested in, then once they were weakened they would take over.

The book starts with an exploration team on a planet that is dead, finding an animal that shouldn't be there and ultimately realized the species was responsible for the demise of the native inhabitants. They return to Earth to find an unusual species popping up, I think in the oceans, that eventually starts to kill off humanity.

The book ends with one of the characters asking the other something to the effect of "will we survive" and the scientist responding "we'll see". Unfortunately I do recall that the book had a very common sounding name, something like "across the stars" or something, so trying to search for it on Google has been impossible.

Answer 1

That sounds like a mash up of the first two books in the "Galactic Center" series by Gregory Benford. Book two is call "Across the Sea of Suns".

The precis of book one is "2019: NASA astronaut Nigel Walmsley is sent on a mission to intercept a rogue asteroid on a collision course with Earth. Ordered to destroy the comet, he instead discovers that it is actually the shell of a derelict space probe - a wreck with just enough power to emit a single electronic signal...

2034: Then a reply is heard. Searching for the source of this signal that comes from outside the solar system, Nigel discovers the existence of a sentient ship. When the new vessel begins to communicate directly with him, the astronaut learns of the horrors that await humanity. For the ship was created by an alien race that has spent billions and billions of years searching for intelligent life...to annihilate it."

The ocean has been seeded with huge weird things/beasts that have caused huge problems with shipping, this is explored more in book two.

Book two, "In 2021, radio astronomy on the Moon reveals the presence of life by a nearby red dwarf, on a tide-locked planet.[1] To investigate, Earth's governments convert a space colony into Lancer, a Bussard ramjet powered interstellar ship based on the design of a crashed alien ship discovered in the Mare Marginis. In 2061, it arrives and discovers a primitive race of nomads, broadcasting using organs adapted to emit and receive electromagnetic radiation. A curious satellite is discovered in orbit, at least a million years old, roughly when a meteor shower destroyed the EMs' civilization."